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Thread: Ground Bus

  1. #21
    Senior Member Bitsyncmaster's Avatar
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    Location:  Leonardtown, MD

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    Quote Originally Posted by Farrar View Post
    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.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  2. #22
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    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:
    GroundBusCombined.jpg

    Bill Robertson
    #5939

  3. #23
    EFI'd dn010's Avatar
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    Location:  Florida: Pinellas County

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    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!

  4. #24
    EFI'd dn010's Avatar
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    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...

  5. #25
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    That plate is the wiper delay ground. The ring terminal on that plate then goes somewhere else.

    Bill Robertson
    #5939

    Quote Originally Posted by dn010 View Post
    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

  6. #26
    Senior Member nkemp's Avatar
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    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
    Last edited by nkemp; 09-20-2011 at 11:22 PM.

  7. #27
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    Do you mean these:

    GroundBusJunctionLug1.jpg

    I buy them at Lowes.

    Bill Robertson
    #5939

  8. #28
    Senior Member nkemp's Avatar
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    My VIN:    897 5 spd,

    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.
    WireClamp.jpg
    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

  9. #29
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    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

  10. #30
    Senior Member nkemp's Avatar
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    My VIN:    897 5 spd,

    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

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