DeLorean Ground Schematic

[content22207]

I am starting to map out all of the ground wires on a DeLorean (the major ones at least), and I've already made an interesting discovery: each set of headlights (and its associated side and front lights) is grounded directly to the bulkhead bolt. These are the seven 12 gauge wires on the bulkhead bolt:
- Left headlight (and side/marker lights)
- Right headlight (and side/marker lights)
- Ground junction behind A/C duct
- Ground junction behind glove box
- Ground junction under console (passenger side, towards rear)
- Ground junction in relay compartment
- Ground junction behind bulkhead connectors

The bundle of wires that everyone gets so excited about on the radio bracket are nothing more than two bit players in the scheme of things.
- Individual panel bulb
- Individual panel bulb
- Individual panel bulb
- Individual panel bulb
- Radio
- Line out
Conventional wisdom that you can correct much of anything by running a large gauge wire from the radio bracket to the body bolt directly below it is total nonsense (unless you've got a big honking radio).

Two of the bigger trouble spots for owners (fuel pump/inertia switch and instrument cluster) are *NOT* grounded to the radio bracket. They come together in the junction behind the A/C duct, then one 12 gauge wire takes them (and a few other things) to the back of the car.

I'll add updates as more & more of #2508's wiring harness is torn apart....

Bill Robertson
#5939

Hold the line on that glove box junction. There is definitely a large gauge wire from the bulkhead bolt to that general area of the car, but there's an identical gauge wire coming off the blower motor -- I need to unwrap everything and see if the blower motor passes through a junction or if it's grounded directly.

Bill Robertson
#5939

[dn010]

This is crazy...so they'd rather run wires back and forth the length of the car to ground things instead of just have a main ground? If it was concerns over cost which prevented them from doing this, I don't see how it would have been cheaper to run all these lengths of wire, cut them, solder them, crimp them, cover them.... they should have just incorporated a separate line in the harnesses [which is obviously what we are doing now] which would have taken less room then dozens single black ground wires that are there now...

By the way, thanks Bill for posting, I'm sure it is taking a lot of detective work and time which you don't even need to do. This is helpful, at least to me it is. Instead of running some select grounds all over the car, I believe I may cut a few grounds (like the headlights) and just route them to the ground bus in their area. Thanks again.

[dn010]

From this discussion, it would be simple to create a diagram. Only thing is that there may be more that have not been discovered yet.

[content22207]

Wouldn't it be great to have a harness diagram showing every wire junction location. I guess this was never a document released from DMC.

I'm working on it:
DeLoreanGroundsInProcess1.jpg

Bill Robertson
#5939

Apparently #2508 has donated its body to science (I am slowly unwrapping its entire wiring harness).

This is what I've got so far:
DeLoreanGroundsInProcess2.jpg

Note the question marks on the last two grounds from the front junction. I'm pretty sure one of them is the windshield wiper motor, but I can't find the damn thing to verify that -- does anybody know where it is? I suspect the other small gauge wire goes to the turn signal/windshield wiper delay chassis, but haven't unwrapped enough to verify that yet.

I'm taking a DeLorean break (these little cars *DO* burn you out), then I will trace down the large gauge wire that passes in front of the glove box. I suspect it's the blower motor.

There are only 5 large gauge wires in the console harnesses before the rearmost junction on the driver's side, all of which appears to come from the ECU compartment. I'll know more after the break.

Bill Robertson
#5939

I'll trace the last few wires tomorrow:
DeLoreanGroundsInProcess3.jpg

Bill Robertson
#5939

These are my ground buses (with the future addition as a dotted line) laid over a working copy of the factory ground schematic:
GroundBusSchematic.jpg
Remember that, except for the headlight extension, my bus is significantly larger gauge than even the factory large gauge wires (4 versus 12).

I now know that making the stainless bar behind the headlights into a ground block was a bit redundant, but it does eliminate the possibility of problems at the washer bottle connector. I may move #2508's trunk light to it for that very reason (#5939's front end is buttoned up, and it's going to stay buttoned up).

My fuel pumps are grounded directly to the frame.

Bill Robertson
#5939

[dn010]

While I do have the continuous length of uncut wire running from bulkhead to the radiator/frame ground - with no breaks or attaching points between the 2 locations (I just didn't think I'd need these in the future) - I didn't opt to ground it to the frame on the bulkhead side. My ground bus runs to the bulkhead junction, from there are 2 more 4 gauge wires - one to the battery and then one to the engine. From the battery, the battery wire runs to the frame so I didn't see a need to ground to it twice.

[Bitsyncmaster]

Good work Bill. If that other ground common to the dash ground is the blower then I will do another frame ground for that.

[dn010]

Bill, can you tell me exactly where the cluster containing inertia switch ground is located behind ac duct? What do I need to take off to see this? I had a hell of a time with the radiator support, the bolt was pretty rusted.so I lost a lot of time getting that removed so I could affix the front of my bus. everything else is all connected for the most part.

[content22207]

The bundle of wires that everyone gets so excited about on the radio bracket are nothing more than two bit players in the scheme of things.
- Individual panel bulb
- Individual panel bulb
- Individual panel bulb
- Individual panel bulb
- Radio
- Line out
Conventional wisdom that you can correct much of anything by running a large gauge wire from the radio bracket to the body bolt directly below it is total nonsense (unless you've got a big honking radio).

Correction: the bundle of wires that everyone gets so excited about on the radio bracket are nothing more than a couple of capacitors, and of course the radio itself.

Individual A/C panel bulb grounds are connected at a junction about an inch or so aft of the radio bracket.

Bill Robertson
#5939

[content22207]

Bill, can you tell me exactly where the cluster containing inertia switch ground is located behind ac duct? What do I need to take off to see this?

Start at the door diodes, then follow the big bundle of wires going up into the dash with your hand and you should feel it.

If you want to use that junction as your grounding point you will probably need to take the seat out so you can lay down with your head under the dash. I was able to manipulate individual wires in the junction to count them, so on #2508 at least it won't be too bad (#2508's steering column is currently out of the car -- don't know if that makes a difference).

The biggest problems seem to be the inertia switch (not a problem for me because my pump is grounded to the frame) and the instrument cluster (lots of owners report gauge problems). I suppose you could simply tap those devices into your bus closer to the source rather than at the junction.

I am going to use the junction simply because it's a cleaner installation. I will use 4 gauge battery cable and a copper lug to be consistent with the rest of the bus.

Bill Robertson
#5939

[dn010]

No wonder I couldn't find it, i was looking on the wrong damn side of the car. Now that I've located it, I'll have to plan a way to ground this to my bus, looks like its going to be a pita but doable. I seem to notice that when I turn things on (car off) I am having much less voltage drops. Especially the headlights and blower, those together used to make the needle sink like a stone, now it barely moves. I cannot compare voltage at the battery since I never measured prior to this work which I wish I had. Ill have the car running either tomorrow or friday to see what my charging voltage and pump voltage is.