Ground Bus

[content22207]

This is an overview of my ground buses (identical on both of my cars):
4396

The bus is 4 gauge battery cable from the top of the engine to the radiator bracket:
4402 4403
then 8 gauge wire to the front of the car (the stainless plate behind the headlights is used as a ground block). Both junctions behind the headlights are tied into the front ground block with 8 gauge wire.

There are 5 ground junctions in the original harness:
- One by the bulkhead connectors
- One in the relay compartment
- Three under the console
These are connected to the bus in their original soldered state:
4397

Wires originally junctioned at the radio bracket have been connected directly to the bus with a bolt. A new wire grounds the radio bracket itself to the bus.

There is a ground block in the ECU compartment:
4400

The relay compartment bracket doubles as a ground block:
4401

The bus has its own connection to the battery:
4404

Bill Robertson
#5939

I just found another ground junction hiding behind the central A/C duct:
4405
This most likely is the ground junction for the inertia switch and the instrument cluster (two trouble spots).

6 of the 7 wires on the rear bulkhead bolt have now been accounted for:
- Junction behind the central A/C duct
- 3 junctions under the console
- Junction in the relay compartment
- Junction by the bulkhead connectors

I will be tying this newly located junction into the front bolts of my ground buses in the near future with short pieces of battery cable (that is why that bolt is there -- to allow me to add grounds to the bus as necessary).

Bill Robertson
#5939

[dn010]

My ground bus is coming along nicely. I took out the 8 gauge because I found 4 gauge $13 for ten feet. So now I have 4 gauge and the console grounds tired in-the ECU bracket, relay compartment and the ground cluster near the back bulkhead all connected too. I see you've found a new cluster which I need to connect, then finish up the front of the car, connect the engine ground and lastly the bus to battery connection and I should be set. I ran the cable to the front of the car by cutting a small hole in the rubber that covers the heating/cooling lines that go through the firewall. I think this is a very easy task, the only trouble I've run into is that the ground clusters have very little wire too work with. Should be done tomorrow and running tomorrow, I'm excited!

[content22207]

I left the junction solder connections intact. They are just pressed against the ground cable. The lug wrapped around them both is copper, so it too is conductive.

Bill Robertson
#5939

[dn010]

I'm using aluminum to connect and didn't have enough room for the whole soldered portion on a few of the clusters, especially the one mid console that has about 7-8 or so wires to it.

[Farrar]

These are the lugs I used to attach my junctions to the bus:

Ah HA! Now it makes sense. I wondered what that square shape was from.

I will look for these the next time I am at the hardware store...

Farrar

Thanks for this thread, Bill! It is most instructive. :)

Farrar

[David T]

The proper way to run a ground for the car would be like the way the + side is done. You run a heavy line from the battery to several posts in different spots on the car. One in the rear by the motor, one under the console, one under the dash, and one under the front. From those posts you connect all of the different circuits. I agree grounding was a neglected area but it works till you have bad connections. Then you get back-feeds and all kinds of weird symptoms. The main ground buss should be one continuous wire with no splices and run inside as much as possible. There are actually TWO grounding systems on the car. One is to run all of the electrical systems. The other is to bond all of the metal body panels together.
David Teitelbaum

[content22207]

The proper way to run a ground for the car would be like the way the + side is done. You run a heavy line from the battery to several posts in different spots on the car. One in the rear by the motor, one under the console, one under the dash, and one under the front. From those posts you connect all of the different circuits....

Um, David, what do you think we're talking about here:
4421

Is 4 gauge battery cable heavy enough for you?

I have two pre-planned access points (three if you count the bolt in the relay compartment, but it is 3/8" diameter which does limit its utility somewhat):
- 1/4" stud in the ECU compartment
- 1/4" bolt used to join two bus segments together at the front of the console
Notice I will be tying the ground junction I found yesterday into the bus at the front bolt.

Bill Robertson
#5939

[dn010]

I made mine one continuous length of wire from the bulkhead to the radiator. From the bulkhead ground point, there [will be] a cable running to the engine, and then another to the battery. I don't think I'll need to access it in the future but in case I do, #1-I attached an extra 10 gauge wire to a few of the attachment points that the ground clusters go to near the front and rear of the console that way I can just tie into that and #2 can always create another point in which to attach more grounds.

[David T]

When I said a continuous cable what I wanted to say is the buss cable should not be cut and terminated at each grounding post but should have a tee type connector that wraps around the cable with a hole in it that attaches to each binding post. This way if any post along the way has a problem with a bad connection it doesn't affect the other junction posts past the bad connection. The buss should also be attached to the frame at each end and at some points between. The way to NOT do it is to cut the grounding buss into pieces and use terminals at each end to connect it to each post.
David Teitelbaum

[Kenny_Z]

Nice, thank you. I'll be able to go further with the grounding I already started.

[content22207]

Today I started making a ground schematic. Learned a few things in the process:
4441
I'll finish it tomorrow.

This is my current bus overlaid on that schematic:
4442
Remember that the bus wires are 4 gauge, not 12 gauge (extension to the headlight ground block is 8 gauge). The junction behind the central A/C duct will be tied in as a future addition, using the same 4 gauge cable and copper lug as all the other junctions (I like symmetry).

Bill Robertson
#5939

[sean]

Feel free to keep Bus talk here but if you want to talk about bill's Ground findings please continue that over here (http://dmctalk.org/showthread.php?1371-DeLorean-Ground-Schematic).

[content22207]

When I said a continuous cable what I wanted to say is the buss cable should not be cut and terminated at each grounding post but should have a tee type connector that wraps around the cable with a hole in it that attaches to each binding post.

Have you read a single word I've written? My console junctions *ARE* connected with a continuous cable, using connectors that wrap around the cable:
4444 4446 4448

There is one bolt in the relay compartment that acts as a central mounting point for cables that are going in 5 different directions (there is no way to run a continuous cable around the relay compartment).

The ECU compartment has a ground block so I could add a 1/4" stud to the bus for future additions (ground bus cables themselves use 3/8" bolts). This block also allows me to attach a cable to the engine -- it's a junction point similar to the bolt in the relay compartment.

As stated, there are no bus junctions underneath the console -- all factory junctions are tied into a continuous wire with wrap around connectors.

At the front of the console the bus is joined with a 1/4" bolt. This bolt is a junction point for wires that used to be attached to the radio bracket (I just moved them to the bolt), and it is a point to attach future wires, such as a cable to a factory junction behind the A/C central duct that I've only recently learned about.

Altogether it is a very neat and orderly installation. It also works fantastically well -- even without the instrument cluster junction tied in I don't have any of the electrical problems that other owners complain about.

Bill Robertson
#5939

[Farrar]

Altogether it is a very neat and orderly installation. It also works fantastically well -- even without the instrument cluster junction tied in I don't have any of the electrical problems that other owners complain about.

I bet your fuses run cooler, too.

Farrar

[ramblinmike]

I've got to hand it to you man, it looks great. Another project on the list!

[content22207]

I will be tying this newly located junction into the front bolts of my ground buses in the near future with short pieces of battery cable (that is why that bolt is there -- to allow me to add grounds to the bus as necessary).

Done (except for wrapping everything up with electrical tape):
4461 4462

Perhaps a little overkill, especially considering that I don't even use that junction for my fuel pump, but I can honestly say, with little fear of contradiction, that I likely have the only DeLorean in the world with EVERY ground junction tied into a 4 gauge ground bus. From bow to stern, every inch of my bus is 4 gauge.

BTW: That junction is *MUCH* easier to access with most of the dashboard out of the way, as it will be on #2508 (after which time there will be two DeLoreans in the world with every single ground junction tied into a 4 gauge bus). I was reduced to working by braille. Removing the plastic shrink wrap over the factory junction was an exercise in patience, but once it was off I knew I was home free.

This addition does illustrate well why I use a bolt to join the console cable to the cable that runs through the firewall.

Bill Robertson
#5939

[dn010]

I can honestly say, with little fear of contradiction, that I likely have the only DeLorean in the world with EVERY ground junction tied into a 4 gauge ground bus. From bow to stern, every inch of my bus is 4 gauge.

BTW: That junction is *MUCH* easier to access with most of the dashboard out of the way, as it will be on #2508 (after which time there will be two DeLoreans in the world with every single ground junction tied into a 4 gauge bus).
Bill Robertson
#5939

In a few hours, there will be 2 Deloreans with every ground tied to a 4 gauge bus... That is, until your #2508 is ready. :cool1: This was definitely worth doing in my opinion.

[dn010]

Bill, did you tie in the grounds that were originally below the ballast resister?

[Farrar]

Here's a question which may possibly be off-topic, but I think it's related:

Where are they relays grounded? It would seem to me it might be easier to take the ground wires of the relay sockets and attach them to the bracket itself, since the bracket is a ground point. But if memory serves, the ground wires from the relay sockets disappear back into the harness. Where do those wires go? In my early car, they're black/red, if that means anything. I ask because I am about to dig in to that area as I re-wire the cooling fan circuit soon.

Thanks,
Farrar

[content22207]

Bill, did you tie in the grounds that were originally below the ballast resister?

Nope. My ballast resistor bracket is electrically neutral (screwed directly to the fiberglass):
4470

The grounds I am mapping out are from the bulkhead bolt forward. My engine compartment is wired radically differently from a K-Jetted PRV. I only have a handful of grounded devices back there:
- Alternator
- A/C compressor
- Choke heater
- Spark plugs
- Starter motor
- Dash gauge sending units
- Whatever else I've forgotten
Believe it or not, for just those few devices, I am running 3 block grounds: the original braided strap, the ground bus already pictured, and this ground cable, added when I did the engine swap:
4471
Suffice it to say, my engine is well grounded, though mostly by historical accident (the driver side cable was added because the braided strap is cheap & flimsy, and I tied in the ground bus by principle).

Bill Robertson
#5939

[Bitsyncmaster]

Here's a question which may possibly be off-topic, but I think it's related:

Where are they relays grounded? It would seem to me it might be easier to take the ground wires of the relay sockets and attach them to the bracket itself, since the bracket is a ground point. But if memory serves, the ground wires from the relay sockets disappear back into the harness. Where do those wires go? In my early car, they're black/red, if that means anything. I ask because I am about to dig in to that area as I re-wire the cooling fan circuit soon.

Thanks,
Farrar

The front row of relays all are daisy chained and one 18 AWG wire back to the group soldered at the rear of the relay compartment. I know this because I rewired the front row grounds. I would assume the back row does the same.

The metal bracket has no connections to ground.

[content22207]

Just taking an A/C break. I'll finish off the schematic shortly.

This is a cross reference between the working schematic, my bus overlay (the cable to the front junction is a reality now), and some of the pictures that have been posted:
4480

Bill Robertson
#5939

[dn010]

Well, there are now 2 DeLoreans with a 4 gauge ground bus. Although my method and set-up is much different than Bills; every ground is attached to it. This took about $65 dollars of hardware and about 6 hours to complete (that includes removing a frozen radiator support bolt, messing with my rack & pinion, and dealing with kids and SWMBO so it probably took much less time)


Findings/ thoughts on the ground bus... I tested how long it took to drain my -already trashed- battery with intervals of 15 seconds (inertia switch tripped) with starter engaged (I have the newer smaller started, not original so you may not be able to compare to me). My starter turned slightly [but noticeably] faster and the battery lasted about twice as long before dying. Voltage drop was less as well during cranking, by at least a volt on my car but I want to test again with a fully charged battery. Once my engine came to life, it ran MUCH more smoothly than it has in years. It also ran steady with no hunt, but I don't know if this really had anything to do with better grounding. Obviously, I had an engine ground issue [among other things] which this has now been corrected - prior to the grounds, when I started my engine it would run like it was firing on 4 cylinders for up to a minute and then fade. I find that my volt gauge reads much higher now, and that (as already stated) when I turn on accessories, the volt gauge doesn't dip as far down. I can compare voltage drops with someone who doesn't have the ground system for actual numbers in different areas/different items. Overall, an excellent upgrade for the money and time it costs. I would recommend this to others. Thanks, everyone -especially Bill, for all your help and knowledge, and ideas!

[dn010]

On another note... When I tied in the ground that is located behind the AC (inertia switch, wiper motor, etc) I removed my AC duct to driver side, the knee pads, and unplugged everything on that side so I could slide the whole wire towards the center of the car. I got a spare 4 inches give or take, so I could hold the ground cluster in my hand comfortably without having to work behind all kinds of components. My problem was that I have an alarm installed, so I had a million wires running around. Guess it was good thing, because I taped them up and made a mess "neat" again.

The grounds that you can't identify likely go to the plate that holds the buzzer and blinker relay as you suspect. I can't imagine where else they would go, and they are of the same gauge...

[content22207]

That plate is the wiper delay ground. The ring terminal on that plate then goes somewhere else.

Bill Robertson
#5939


On another note... When I tied in the ground that is located behind the AC....

Until recently I had no idea that junction was even back there. For many years owners have struggled to find ways to better ground the instrument cluster. Running a heavy gauge wire from the radio bracket to the body bolt below it was one of the most popular. Conventional wisdom held that the instrument cluster was grounded via the radio bracket. Now we now that isn't the case. In fact, the radio bracket is a very minor player in the grounding scheme of things.

Same with the radiator bolt. I have seen owners attribute all sorts of things to that bolt. Other than the radiator fans, it too is a minor player.

The conventional wisdom of "cleaning all your grounds" is pretty much debunked as well. As far as the carbody is concerned, there are only two grounds to clean: the radiator bolt and the bulkhead bolt. As you saw, every junction inside the car is soldered together -- there's nothing to clean. Dirty grounds aren't the problem -- undersized wire and ganging too many devices (especially the junction behind the A/C duct) are.

I am very pleased that my ground bus has a totally weather tight connection to the battery. Doesn't matter how funky my trailing arm bolt gets -- I will always have a perfect battery connection of exactly the same gauge wire. Same with the engine block (it is not totally weather tight, but it is on top of the engine rather than right next to the street). I will most likely never "clean my grounds" because I don't have to.

Bill Robertson
#5939

[nkemp]

Bill ...What are those connectors? Where did you get them?

I checked a couple local stores but nothing like what is shown. The closest thing I could find required part of the base to be sawed off.

Nick

[content22207]

Do you mean these:

5305

I buy them at Lowes.

Bill Robertson
#5939

[nkemp]

I used clamps like in the photo. They disassemble and slide over the wires. A bit larger than your solution but they work... and the larger size allow lots of wire in the clamp.
5378
For the bus I used the black wire from 4 gauge jumper cable (clamps removed). I also bought some 10 Gauge jumper cables ($5 ) for runners off the bus. Jumper cable is easy to work with ... very flexible.

$2 at the junkyard got me a negative battery cable that runs from the bulkhead stud to the negative terminal.

The ground to the engine is the existing wire from the bulkhead bolt to the engine (that connection to the engine is the one that was causing rough idle last year and caused the D to die the other day. Corrosion problems.)

For those looking for the ground junction behind the panel... mine was straight up from the accelerator. There are 2 or 3 other powered(non-ground) junctions in the same area.

Since the bus has been installed, I noticed
- An immediate improvement in the Volt gauge. It is much more accurate.
- The voltage does not drop with the lights on ( the headlights are not bussed in yet).
- The radio seems less noisy (less static)

Nick

[content22207]

Each headlight has an almost dedicated (shared with the front and side marker) ground wire to the rear bulkhead bolt. Other than the harness connector under the washer bottle, it's an uninterrupted connection. If you ever have your headlights out you can reground them differently (why not?), but until then they should be fine.

You are 100% correct that the ground junction behind the A/C duct is inadequate. Everything in front of the driver shares a single ground wire, including the fuel pump, which is probably what kills Fuse #7 and the inertia switch.

Bill Robertson
#5939

[nkemp]

I think it is worth mentioning that even though a car has a ground bus installed, it is still important to maintain the original ground from the negative battery terminal to the trailing arm bracket bolt. When you have a ground bus, you have a parallel ground circuit assuming that the bus is attached to the radiator bracket. One path is the bus, the other path is via the frame to the trailing arm ground.

If the ground connection is lost at the TA bracket (I've had that happen on a tight metal on metal connection probably due to galvanic action), then the starter and other engine related currents will follow the frame to the radiator bracket, to the ground bus to the battery. The starter current is the only significant load, I presume the 4gauge bus will carry it but it is a long run of 4gauge.

To the extent that there is resistance (corrosion or wire length) on the paths, the two paths share the current load per Ohm's law. In other words, the ground bus carries a portion of the fuel pump (selected purely as an example) current as does the frame (again assuming that the ground bus is attached to the radiator bracket & the negative battery terminal). The extent to which each carries some load is a function of the path resistance. Bad junctions such as potentially at the TA bracket bolt increase resistance and alter the amount of current on each path.

CONCLUSION: even with a heavy duty ground bus, maintain or improve the ground connections at the TA bracket, engine and or transmission.

Next week I'm off to the scrap yard for another negative battery cable as a jumper from the TA bracket to the Transmission... and I may even consider a continuous wire or soldered connection from the battery negative to the TA bracket to the transmission just to avoid the possibility of corrosion at any junctions.

Nick

[Bitsyncmaster]

I think it is worth mentioning that even though a car has a ground bus installed, it is still important to maintain the original ground from the negative battery terminal to the trailing arm bracket bolt. When you have a ground bus, you have a parallel ground circuit assuming that the bus is attached to the radiator bracket. One path is the bus, the other path is via the frame to the trailing arm ground.

If the ground connection is lost at the TA bracket (I've had that happen on a tight metal on metal connection probably due to galvanic action), then the starter and other engine related currents will follow the frame to the radiator bracket, to the ground bus to the battery. The starter current is the only significant load, I presume the 4gauge bus will carry it but it is a long run of 4gauge.

To the extent that there is resistance (corrosion or wire length) on the paths, the two paths share the current load per Ohm's law. In other words, the ground bus carries a portion of the fuel pump (selected purely as an example) current as does the frame (again assuming that the ground bus is attached to the radiator bracket & the negative battery terminal). The extent to which each carries some load is a function of the path resistance. Bad junctions such as potentially at the TA bracket bolt increase resistance and alter the amount of current on each path.

CONCLUSION: even with a heavy duty ground bus, maintain or improve the ground connections at the TA bracket, engine and or transmission.

Next week I'm off to the scrap yard for another negative battery cable as a jumper from the TA bracket to the Transmission... and I may even consider a continuous wire or soldered connection from the battery negative to the TA bracket to the transmission just to avoid the possibility of corrosion at any junctions.

Nick

Agree. I need to do a measurement of the resistance of the frame someday. Yes steel is a poor conductor compared to copper but with all that area in the frame it may not be aiding you much to install a copper ground buss. The buss does make less voltage drops if you rewire your existing circuits to it. It makes it easier than using the frame as the buss.

All I need to do is measure the voltage drop from the front frame terminal to the rear frame terminal (TAB) with the fans running. Then knowing the current draw on the fans I can compute the resistance of the frame. Then I can compute the resistance of a #4 AWG copper wire and see what that in parallel will buy you.

[content22207]

I think it is worth mentioning that even though a car has a ground bus installed, it is still important to maintain the original ground from the negative battery terminal to the trailing arm bracket bolt.

Not if the bus has its own connection to the battery.

I could disconnect all original frame ground points and my car would operate exactly the same. Every one of them has been rendered redundant.

My new battery to bus connection is far superior to the original trailing arm ground because:
- Terminals are soldered on both ends
- It is located inside the car (weather tight)

Bill Robertson
#5939

[nkemp]

I like your ground bus and have added it since my last dead D experience this week. I have planned on doing so for a while and wish I had done it sooner.

If I understand the bus in your car:
- You have a new ground from the bus to the engine
- The bus also connects to the frame at the radiator bracket

If correct then yes you can disconnect the TA ground. Now one needs to maintain the grounds at the engine and potentially the front bracket (both subject to the weather). The ground at the engine from the bulkhead ground is what caused my D to get the nice guy with the flatbed to give me a not-free ride home the other day (lost the fuel pump ground circuit).

The problem we face when grounding to the engine or frame is galvanic corrosion. Combinations of aluminum, copper, zinc, steel, water, electrical flow and oxygen results in "activity". (As I recall, aluminum & copper is especially bad)

Your ground bus is superior to the original and the community is better off with this knowledge. I still think we must remember that the connection points at the frame &/or engine are not trouble free. We need to maintain those points or develop a better method. I prefer the latter.

Nick Kemp

[content22207]

I'll be damnded if I am going to lay on the ground and mess with the original frame to battery ground. Same with the original braided strap. If they work, great. If they fail, I'll never know it.

My engine is actually grounded three times:
- Original braided strap
- 4 gauge cable on the other motor mount (installed before my bus):
5410
- Ground bus
5411

I have no intention of even thinking about my DeLorean grounds through the next decade or two of ownership.

Bill Robertson
#5939

[1batt4u]

I bought the 2 battery cables from John Hervey. I know one replaces the one on the chassis, right next to the coil. Where does the other wire go?

[stevedmc]

I bought the 2 battery cables from John Hervey. I know one replaces the one on the chassis, right next to the coil. Where does the other wire go?

It is basically an extension that runs to the transmission.

[1batt4u]

Is this it??

http://i53.tinypic.com/5anw9z.jpg

[Ashyukun]

Is this it??


Nope- that's the stock frame-to-engine block ground, though the second run of wire in Hervey's kit does somewhat duplicate its functionality by hooking up the ground to the transmission, which is of course bolted fairly securely (or should be, at least...) to the engine. One end of mine is hooked up to TAB bushing connection along with the line from the battery, and the other end I found a convenient bolt on the transmission to pull, clean off, and bolt the ground to it.

[aludden]

So, how did you traverse the fiberglass?
. Relay box to bulkhead connector
. ECU compatment to engine
. Dash to radiator bracket
. Battery to Relay box

Did you drill holes?
Thanks!
Alex

[Farrar]

Bill's not here so I will try to answer that question for Alex.

I believe most of the people who have done ground bus runs have had to drill holes in the fiberglass, because the wire they were using was so thick it couldn't be threaded through existing grommets. Also, I think Bill's version of a ground bus also grounds the metal bracket behind the passenger seat (similar to the grounding of the bracket behind the driver's seat). Of course, you can go about it in a different fashion. I think the idea is sound, but 4 AWG wire is a bit overkill in my opinion. ;)

I hope that helps!

Farrar

[aludden]

Bill's not here so I will try to answer that question for Alex.

[...]
I hope that helps!

Farrar

Thanks Farrar! I forgot Bill is in England.
I did buy some 4GA wire, but it turned out to be more like 6GA (less overkill?).
I guess everyone does things a little different, and so will I. But the whole idea appeals to me, so I'm going with it. I don't want to drill unnecessary holes if there is a better way, so I was hoping for some pictures/explanations of what others had done.

[dn010]

I can't remember whether I drilled a hole or used an existing one to get from the inside of the car to the outside under the trunk compartment (Front of car) - worst case I only had to drill one hole. For the rear, there is already a ground point that goes through the fiberglass and into the coil area - you can just use that to get from the inside rear to engine compartment.

[aludden]

I can't remember whether I drilled a hole or used an existing one to get from the inside of the car to the outside under the trunk compartment (Front of car) - worst case I only had to drill one hole. For the rear, there is already a ground point that goes through the fiberglass and into the coil area - you can just use that to get from the inside rear to engine compartment.

Thanks! I'll need to look more closely at that coil area bolt. I guess it is behind the parcel area back wall.

Actually, I was thinking of maybe running the wire through the same hole that the battery cable is going now, on to the engine or transmission, and then up to the ground bolt on the chassis under the coolant bottle, which ties to the coil area bolt.

[dn010]

You'll need to take the rear bulkhead panel off - just unscrew the brackets that hold the cargo net just beneath the rear window and pull the panel out. This will expose a few ground points you'll want to tie into the bus. I kind of followed Bills lead when he was doing this - I just used a different method of bringing it all together than he did. He did all the investigation work as far as where all the ground points are - I doubt I would have done as much as I did if he didn't begin this. Anyway, It is easy and takes a few hours if you have all the items you need. If you decide to drill thru the fiberglass, all you'll need are some grommets and you're good to go.

[aludden]

You'll need to take the rear bulkhead panel off - just unscrew the brackets that hold the cargo net just beneath the rear window and pull the panel out. This will expose a few ground points you'll want to tie into the bus.
[...]

I had read about those other grounds behind the panel but had no info. OK, off the panel goes!

Thanks!
Alex

[aludden]

OK, I installed a similar bus! However, I could not find two of the grounds that Bill mentions:
. He has 4 ground junctions in the center console - I only have 3: one in the back, one about a foot from the back on the opposite side, and one by the radio bracket.
. I did not find the one above the pedals, behind the ac duct. My whole dash is out, so I got a good look. Nothing resembling Bill's picture.

I have an early VIN 1968, so maybe things changed later?

[dn010]

I had such a hard time finding the "above pedals" ground that I started to believe it did not exist! It took a while but I finally was able to locate it. It was more behind the A/C housing than it was the pedal box. I removed the duct work running above the steering column and tugged the whole harness towards the driver side of the car exposing the cluster. I found it by running my hand up the harness.... I'd imagine it is the same on your vin; I'm not sure where else they would have grounded those components.

My memory is not terribly reliable, especially on a Saturday night, but after looking at the pictures of my own ground bus system - I believe the 4 main grounds under the console are as follows: 1- one in back by idle ECU; 2- one in middle approx where the window switches would be; 3- one near the radio bracket - *4- all the wires that attach to the radio bracket itself.

Good luck on this, let us know how it goes!

[aludden]

I had such a hard time finding the "above pedals" ground that I started to believe it did not exist! It took a while but I finally was able to locate it. It was more behind the A/C housing than it was the pedal box.
[...]

My harness doesn't go behind the a/c housing at all. It comes from the console hump and goes up and goes between two metal plates above the steering wheel. There's a green wire junction and a striped one, but no black. It is probably between those two metal plates. I tried getting my hand in there, but I could not feel any junctions as far as I could reach. There's one single black wire which goes to a single connector up there, too hard to reach.

As far as the other missing ground point, from looking closely at Bill's pictures I guess it's not a ground point but just a junction he did near the shifter, between the one by the cigarette lighter and the one by the radio bracket, so nothing really missing there, I just don't have that.

I ran mine as one 24' wire from the battery to the radiator bracket, and I went through the front wall with the speedometer cable. The only hole I drilled was in the plastic roof piece from the battery compartment to the relay compartment. I will do a separate wire from the battery to the engine block or transmission.

The hardest thing in the whole job is cutting the insulation in the wire without damaging too many (very) thin strands. It might have been easier if the strands were thicker, but then the wire would be stiffer also...

[dn010]

I'll look at mine again tonight and see what it looks like. I did this a while ago so I can't remember correctly where everything was; in fact I feel terrible I haven't worked on my D in months:facepalm:. I do remember finding that green cluster of wires and wondering if that was it but I kept searching. - From what you say it does in fact seem that there was a totally different wiring harness in early vin compared to the later ones - IIRC even the '83s have different rear harness than the rest. Glad to read your method of doing the bus, it adds to the possible ways of running this thing from the front to rear of the car successfully. I ran my from the battery to the ground junction behind the rear panel (had to drill a hole in the relay compartment to run the wire from the battery compartment thru relay compartment and up to the junction) and then from the junction over around to the idle ECU compartment and followed the harness up, likely drilled a hole in the fiberglass and out to the radiator bracket. My cable was made up of thick gauge wire so running a razor blade around it took the insulation right off. I used an automatic wire stripper for the small gauge car wires. Just remember, there is no point in doing a ground bus if you don't tie in all the grounds. I know once I got mine alive after the bus - there were many noticeable differences from brighter lights to a higher reading on my volt gauge; not to mention the correct voltage at the fuel pump - which was the whole reason I did the ground bus in the first place! Let us know how it comes along, and what your results with it are. -----Dan

[aludden]

Well, hot dawg! You're all absolutely right. I had given up on it, and today decided to take one more look. It turned out to be on the back side of the harness, against the wall, with a plug for other wires taped in front. Really difficult to reach, but I managed to remove the cap and take some of the really hard insulation off of the ground bus wire near it. My harness doesn't quite run the same as in Bill's pictures - it's further back and not as accessible. Tomorrow I need to go buy another split bolt, as I had used them all up. It will take some work to get it tied, but I will then have them all!

I also noticed a couple of other grounds: a couple of wires together on one of the dash bolts by the glove box, and the heater fan has three or four ground wires that come together as well. I may just run a thinner wire to them, connected to the bus at the radio bolt.

Thank you all!
Alex

[todd1561]

Where do people recommend getting the 4ga wire and roughly how many feet should I plan on buying? Can I substitute jumper cable wire assuming it's solid copper? Seems to be a better cost per foot.

[Bitsyncmaster]

Where do people recommend getting the 4ga wire and roughly how many feet should I plan on buying? Can I substitute jumper cable wire assuming it's solid copper? Seems to be a better cost per foot.

I used these guys for battery cable and large terminals.

http://www.delcity.net/catalogdetails?item=5214205

[Farrar]

I got mine here (http://www.wiringproducts.com/6-awg-gauge-black-battery-cable). Pretty sure I bought copper lugs from the same supplier. But it was a while ago now.

[madstudios]

I’d like to thank everyone here, I’ve just installed a 4 gauge ground bus on #3772. Thanks again for all the details and explanations!


Enviado do meu iPhone usando Tapatalk

[Shep]

Glad I saw this bump, need to add something:

The alternator should also be included on this "bus". In car audio circles, it's called the "big three" upgrade -- grounds between 1) alternator, 2) battery, and 3) frame. With the ease of corrosion on the OEM frames, as well as the car's quite electrically insulated construction between compartments, this really needs to be emphasized more than it is now. Too many frames are being decimated from rust, and truth be told, channeling the entirety of the car's grounding through the frame is a contributing factor.

I would personally argue however that while this will definitely help, for the distance involved, 8 AWG is not going to matter much when placed next to the frame. 1/0 AWG or bust from front to back of car. Headlights and radiator fans alone are going to draw 8 AWG to its max or beyond even, I would be surprised if HVAC and radio don't combine to max out 4 AWG, then there's the fuel pump and clock and external lights and other lower-power devices and you're better off leaving capacity here. 2 AWG is not that much bigger than 4 AWG, and almost nobody carries it for that exact reason (it took me a month to source some myself actually).

Part of the point of the Big Three is to eliminate as much of the "stressful" load off of the frame as possible, not just to beef it up. This allows your frame to be the structural integrity of the car, not the electrical integrity that it was never designed to be. This means 1/0 AWG needs to go from battery to front of car also. It's an investment, yes, but it's a one-time. 8 AWG is seriously undersized for the distance involved and current required.

One last note: don't skimp on the wire branch points. I personally always recommend a proper solder joint these days (used to swear by crimping, but too many issues led me to change that), electrical tape around the branch and secure with heat shrink tubing. Always works wonders and looks quite professional

[Bitsyncmaster]

In stock wiring, the headlights run their ground through the connector at the washer bottle and back to the relay compartment with two 12 AWG wires. I don't know why they did not use the frame for ground like they did with the fans. I,m guessing they were planning on a headlight control or burned out bulb warning.

I rewired my car to use the frame for the headlight grounds. That reduced a lot of ground power back in the relay compartment. It also gives you two extra wires up front if you need power up there.

[Nicholas R]

The only way you're going to keep current from going through your frame is if you actually isolate the frame, which is very unlikely. On something like the alternator, this would only be possible if you mount the alternator using all non-conductive bushings and hardware. You can add a ground wire of whatever size you want, but since nearly all alternators ground through the housing, you're still going to have parallel paths between the wire and the mount. A simple resistance comparison would tell you proportionally how much current will go through each path. If you want to control corrosion on your frame, the best way is to keep your ground points as clean as possible (preferably covering them with dielectric grease every so often).

[Shep]

Fully eliminating power from the frame is not the goal, nor is avoiding corrosion. The goal is to allow the full car's current to utilize these ground wires if it so chooses, and to properly (or over-) size the wiring so that grounds are never restricted. With the sheer number of reports on bad grounds, I have been of the thought that an approach like this, which includes the alternator via an eyelet on the mounting bolt, is ideal ever since I learned about it. It beefs up the cars grounding system which time has shown to be problematic.


Most of this is parallel, but the rest is adding connection points that are often overlooked. That's what the "big three" is all about. It will assist in preventing corrosion, but this is not an answer to frame rust, nor will it ever be. It helps about as much as rising your frame off with a garden hose annually, let's be honest, which is to say yeah it can help, but there's far better uses of your time and energy if that's what you're looking to get out of it.

[Farrar]

I'm no electrical genius, so can someone please explain to me how grounding the alternator via a cable is better than grounding the alternator via the engine? How does cable > engine in this instance? Thanks in advance.

[Ron]

I'm no electrical genius, so can someone please explain to me how grounding the alternator via a cable is better than grounding the alternator via the engine? How does cable > engine in this instance? Thanks in advance.Think of killing an ant with an atomic bomb....:devil:

[Farrar]

Think of killing an ant with an atomic bomb....:devil:

A friend of mine likes to say "Overkill is underrated." ;)

[Bitsyncmaster]

Your starter also relies on the contact of engine to ground it. The extra ground wire just provides a path if the contact surface was not clean or the bolts are loose.

[Nicholas R]

I'm no electrical genius, so can someone please explain to me how grounding the alternator via a cable is better than grounding the alternator via the engine? How does cable > engine in this instance? Thanks in advance.

Personally I don't think it is. I don't know of any production vehicle that doesn't simply ground the alternator through the housing of the alternator, to the engine block. Older vehicles with external voltage regulators may be different, but any modern single wire alternator grounds through the alternator housing.

[FABombjoy]

I'd guess the only exception being if you engine ground strap rots out. Isn't that what sets shift cables alight?

I did add a cable from the alternator housing to the frame. It was cheap & easy as my CS130 alternator already had a ground cable/strap bolt. I wouldn't have gone out of my way to add one tho.

Ground wise, this is what I did:
-Alt case ground - because cable was cheap & flat was there
-4ga lead from the bulkhead bolt directly to the battery - The ground wire connecting to the bulkhead bolt to the frame seemed flimsy to me considering how close the battery is.
-Additional block ground strap on drivers side - Easy to do when changing the motor mounts

+12 side:
-I binned the triple brown alternator wire world tour that runs across the top of the engine. Jump lead is now connected to the +12 bulkhead bolt in the '83 style

Basically just skosh of cheap overkill.

Megasquirt voltage & sensor logs are clean as a whistle. Audio system (amp connected directly to the bulkhead bolts) has no perceptible hum/buzz/whine/etc.

[Ron]

I'd guess the only exception being if you engine ground strap rots out...

And guess what the starter is going to try drawing 100++ amps through ;-)


I binned the triple brown alternator wire world tour
:hysterical:

That and a cable connecting the block directly to the battery should be on any D upgrade list, imho!

[Shep]

I'm no electrical genius, so can someone please explain to me how grounding the alternator via a cable is better than grounding the alternator via the engine? How does cable > engine in this instance? Thanks in advance.Personally I don't think it is. I don't know of any production vehicle that doesn't simply ground the alternator through the housing of the alternator, to the engine block. Older vehicles with external voltage regulators may be different, but any modern single wire alternator grounds through the alternator housing.

Just so everyone's on the same page, electrons flow from ground to positive. The mix up was because some idiot way back when flipped a coin and got it wrong and we all hate him forever for it. Anyhow. When you're trying to water your flowers, do you turn the spout on and hope it will eventually reach your flowers, or connect a hose first and at least guide it to the flowers? Same principle here. It works without a hose, but it's not at all efficient by any stretch of the imagination.

Ron's bit on the starter is spot on with the reasoning as to why the Big Three is around at all. It increases efficiency of the electrical system by allowing surge current and voltage to flow unimpeded. Ever had a low battery cause a difficult start? Same basic concept: the overall capacity isn't there. The system struggles to get enough current from the battery to start the car. With the car's wild mix of metals and material choices along this grounding path, there's not much sense in reinventing the wheel. Engines are aluminum, frames are steel, painted with epoxy, wires are copper, even the electrons don't know what the hell they're doing. Start to finish one-piece wire eliminates any question marks, maintains reliability, and provides an easy path of least resistance.

So, why don't production guys ground with wires by default? They... actually do, I don't know what makes anyone think they don't. Alternator grounds to the engine. Engine grounds to the frame. Via a wire. The Big Three leaves that ground wire for spark plugs, ECU, transmission governor, etc. functions alone and instead adds a new wire bolted directly onto the alternator mount. The alternator is creating electricity, so it really needs its own set of grounds to battery and frame. The reason automotive manufacturers aren't squeezing 100% electrical efficiency out of their cars from the factory is extra cost for zero benefit for them. 99% of the population daily drives their cars and doesn't care about this stuff. Why cater to the 1% of customers that do, and will likely redo it anyway? Much like putting plastic speakers in the cars, nobody cares enough to say they sound horrible because it sounds fine to them.

I know I redid my car's attempt at the Big Three though. My 2017 Kia Optima has a wire grounding the battery to the frame within 12 inches. But with 8 AWG, it wasn't long at all before I upgraded it, and extended it also to bolt to the alternator at the frame mount. While not ideal (it's missing the alternator-to-battery wire), I will have to revisit at a later date when I can get a new battery in the thing. Yes, it's new, but lead acid batteries are a whole 'nother shitfest of their own.

[Farrar]

Thanks for the info. 👍

[NckT]

7 pages of posts to add extra earth (ground) points, when all that is really required is to clean up any high resistive joints on the original wiring on the car.

[Shep]

7 pages of posts to add extra earth (ground) points, when all that is really required is to clean up any high resistive joints on the original wiring on the car.God no, nonono no, don't encourage bad behavior, that's like brushing your teeth and leaving the cavities alone, then chowing down on a bowl of popcorn kernals mixed with ice. None of that is even remotely close to a good idea. It's more akin to a band-aid on a broken femur than a legitimate solution to a design flaw.

I don't think anyone at any point in this thread has said that only cleaning up "high resistive joints" alone is a even close to a wise idea for good reason. The first post was about laying down new ground wires to compensate for the undersized OEM ones. Where the notion came from that the car's grounds are properly designed is beyond me but they are anything but.

Steel is tolerable as a wiring path, but only if properly cared for. McFly himself saw exactly why grounding through the easily-rusted frame is a horrible idea. Modern manufacturers do it because unibody designs inherently mean that frame and body are one electrical channel. That's why batteries often ground to the mating section between unibody and frame. And it's also why said ground is physically built far away from potential sources of corrosion, which places it under the hood of the car.

The DeLorean did a lot of things wrong with the electrical approach by design. First, the frame is the only stretch of wire front to back in some ground loops. This is a terrible idea when high current devices (headlights, fans) are using this very same path. A chain is only as strong as its weakest link. The mere fact that the weakest link needs occasional redoing to keep pristine speaks volumes.

Bear in mind also that automatic frames have a different current capacity than manual frames thanks to the transmission shifter cutout. It's equivalent to a kinked pipe, there's an immediate loss in capacity at that spot. I'd personally estimate that section of frame gives an equivalent AWG size between 1/0 and 2 for copper wiring, given the difference in metal as well as conductivity of copper vs. mild steel, as well as a corrosion factor to accommodate most frame conditions.

This was an area that DMC would have worked out had they been given adequate time and resources to do so. I'm convinced that Johnny Carson's infamous hitchhiking could have been at least partially alleviated with more focus on the electrical system. Some who have crunched the numbers have stated the alternator was more than capable of handling the load, and wondered why it didn't. What's forgotten is the current doesn't travel to the front that well, which is exactly where all the power was being used.

[Bitsyncmaster]

I did run an extra ground wire on the drivers side frame to engine mount but that was because I could not verify the passenger side was clean and a good ground.

The one ground I found that was a poor design was the fuel pump current sharing the ground for the gauges. The added current from the fuel pump creates a voltage offset for the gauge ground. Hence our volt gauge reads about 0.3 volts to low.

[NckT]

God no, nonono no, don't encourage bad behavior, that's like brushing your teeth and leaving the cavities alone, then chowing down on a bowl of popcorn kernals mixed with ice. None of that is even remotely close to a good idea. It's more akin to a band-aid on a broken femur than a legitimate solution to a design flaw.

I don't think anyone at any point in this thread has said that only cleaning up "high resistive joints" alone is a even close to a wise idea for good reason. The first post was about laying down new ground wires to compensate for the undersized OEM ones. Where the notion came from that the car's grounds are properly designed is beyond me but they are anything but.

Steel is tolerable as a wiring path, but only if properly cared for. McFly himself saw exactly why grounding through the easily-rusted frame is a horrible idea. Modern manufacturers do it because unibody designs inherently mean that frame and body are one electrical channel. That's why batteries often ground to the mating section between unibody and frame. And it's also why said ground is physically built far away from potential sources of corrosion, which places it under the hood of the car.

The DeLorean did a lot of things wrong with the electrical approach by design. First, the frame is the only stretch of wire front to back in some ground loops. This is a terrible idea when high current devices (headlights, fans) are using this very same path. A chain is only as strong as its weakest link. The mere fact that the weakest link needs occasional redoing to keep pristine speaks volumes.

Bear in mind also that automatic frames have a different current capacity than manual frames thanks to the transmission shifter cutout. It's equivalent to a kinked pipe, there's an immediate loss in capacity at that spot. I'd personally estimate that section of frame gives an equivalent AWG size between 1/0 and 2 for copper wiring, given the difference in metal as well as conductivity of copper vs. mild steel, as well as a corrosion factor to accommodate most frame conditions.

This was an area that DMC would have worked out had they been given adequate time and resources to do so. I'm convinced that Johnny Carson's infamous hitchhiking could have been at least partially alleviated with more focus on the electrical system. Some who have crunched the numbers have stated the alternator was more than capable of handling the load, and wondered why it didn't. What's forgotten is the current doesn't travel to the front that well, which is exactly where all the power was being used.

With the greatest of respect, analysing and testing the existing wiring on mine and others cars is not "bad behaviour", adding additional cabling to compensate for existing faults is. The only way I see this is a gain is that a product is made to realise money that is easily fitted by non technical people to see a "result" afterwards.

The only really undersized gauge wire is what Dave mentioned, this is the only one that needs a separate earth (ground) wire.

[Shep]

With the greatest of respect, analysing and testing the existing wiring on mine and others cars is not "bad behaviour", adding additional cabling to compensate for existing faults is. The only way I see this is a gain is that a product is made to realise money that is easily fitted by non technical people to see a "result" afterwards.

The only really undersized gauge wire is what Dave mentioned, this is the only one that needs a separate earth (ground) wire.Okay, this is counter to how your prior post read. More than just fixing the high impedence grounds, visual + electrical inspection of related grounds as well as diagnosis / prevention of impedence is also required (yes, required in my book -- this doesn't have to cost money and really is preventative maintenance at that point). Omitting that was what I was calling "bad behavior", I'm getting the vibe now though that you were referring to that along and I misread that -- my apologies!

I can tout the benefits of the Big Three all day long, but unless you're doing a lot of high current stuff, it's likely to not be terribly beneficial. But again, tackling this as a "while you're in there" hasn't stopped me before personally. Particularly if one ground cable has issues multiple times, it is worthwhile swapping it out and checking it regularly. I want to say there was some steel used in the DeLorean ground wires from the factory, I could be mistaken however. For a setup that sees corrosion, any chronically faulty high-impdence ground should be swapped with an equal or bigger wire of non-corrosive material.

I will note that some of the vendors do this type of work, but don't sell the parts. Reason being, it's a niche inside of another niche, and wiring is available damn near anywhere. Just cut to length and install. It's also one that is highly a matter of preference for how it's done. They'd sell maybe ten sets at ten different sizes, why bother if we source it ourselves anyways?

It was also news to me that the radio taps into the frame and out to the battery/alternator, but does make sense. That's the one stretch I would patch with a 4 AWG or higher ground cable if you upgrade the radio. Modern radios pull more current than stock, often come with amplifiers built-in, for the short distance you're also bypassing the transmission cutout and allowing everything up front to piggyback off it. There isn't much harm in this approach, and will suffice for 99% of drivers out there.

For the extra 1%, beef up :)

[NckT]

If you're going to add cabling, don't forget to include for internal resistance of the cable based on the resistivity of the material used and the internal structure of the calling too ie number of stands/core diameter etc with your calculations.

[Bitsyncmaster]

If you're going to add cabling, don't forget to include for internal resistance of the cable based on the resistivity of the material used and the internal structure of the calling too ie number of stands/core diameter etc with your calculations.

I ran a test way back when Bill suggested this ground buss. I remember reading the voltage drop over the frame with a known current flowing. With that result I computed the resistance and suggested only a 2 AWG wire or larger would make any difference.

So what runs off the frame ground. Cooling fans and blower motor seem to be the only thing up front. So do you really need to add a few millivolts to those loads?

[NckT]

I ran a test way back when Bill suggested this ground buss. I remember reading the voltage drop over the frame with a known current flowing. With that result I computed the resistance and suggested only a 2 AWG wire or larger would make any difference.

So what runs off the frame ground. Cooling fans and blower motor seem to be the only thing up front. So do you really need to add a few millivolts to those loads?

I'm glad you've got my point Dave and have done realistic computations.