Electrical Grounding

[Regulus]

Hello again everyone,

Nice to have the forum back, for a couple of months I thought that Delorean ownership had plunged back into the info-vacuum of the 1990s.

Question for everyone; I've been trying to solve a ground problem somewhere in my car since I bought it. The problem is only pronounced when the AC compressor is engaged. To solve this problem, i've re-grounded the battery ground from the frame to the transmission directly. This seemed to help, but didn't solve the problem completely.

Any other tips on re-enforcing the ground on the car's electrical? should I ground the battery directly to the frame and transmission? I already cleaned the engine-to-frame ground strap, plus a raft of other grounds, but can't seem to find the fault.

Any Ideas?

[Bitsyncmaster]

What makes you think you have a ground problem?

The Starter, alternator and AC clutch all require their case have solid grounds. The get the grounds by case contact to the engine or mounts to the engine. You have to make sure there is no paint or corrosion on the metals where they mount to the engine.

[Regulus]

Hi Dave,

This is the same A/C problem I've had for about 3 years now. the electrical is fine until the compressor is energized, or more precisely, until the compressor clutch disengages. that sends a spike thru the system. On my 140amp DMCH alternator, this manifested itself as a 1 second idiot light flash timed with the compressor disengagement. With a 110 amp Pj Grady Alternator, it was generally asymptomatic for about 10 mins, when it then died. the alternator came back for about 2 mins, then froze totally open, sending 18volts plus to the battery! total regulatory failure. I know that regulator hate bad grounds, which leads me to think its a ground fault. i have the 140amp on there now, but have had the regulator of the 110 amp rebuilt. even with the battery grounded directly to the transmission case, i have had no luck.

since it is only the compressor that is problematic, should i look to unmounting, cleaning, then remounting? I just can't see how the compressor would lose ground to the block overtime, its on there pretty good.

Any thoughts?

Thanks

[content22207]

Run a 2 gauge battery cable ground bus from the front of the car to the rear. Tie every single ground junction into the bus. Of course attach the bus directly to the battery. Only costs $20 or $30 and eliminates all electrical anomalies.
GroundBusEngine.jpg GroundBusEcuBlock.jpg GroundBusRelayBolt.jpg GroundBusRearFrameBundle.jpg GroundBusConsole1.jpg GroundBusConsole2.jpg GroundBusConsole3.jpg GroundBusFrontRadiator.jpg

Bill Robertson
#5939

[Ron]

Any thoughts?

Like Dave said, it would help to know what makes you think you have a ground problem... It sounds like your battery/alternator may be too weak to handle the demand when the compressor kicks in...stock cooling fans (power hogs) automatically come on at the same time.
You might try connecting one end of a (quality) jumper cable to the battery (-) and connect the other end to suspect ground points while the problem is present while watching for a change in the symptom.

[Regulus]

It sounds like your battery/alternator may be too weak to handle the demand when the compressor kicks in...stock cooling fans (power hogs) automatically come on at the same time.

I replaced my stock fans with Wings-B-Cool fans from DMC NW, all the lights are LED on the car, JOE Cool installed. Basically every amp saving device is on the car. Oh, the battery is a Optima red top, alternators were brand-new when installed.

I do like your idea of running a ground from the battery to the compressor directly. I will definitely try that.

If it's not a ground, why else would the compressor cause such an electrical disturbance when releasing the clutch?

[Ron]

I replaced my stock fans with Wings-B-Cool fans from DMC NW, all the lights are LED on the car, JOE Cool installed. Basically every amp saving device is on the car. Oh, the battery is a Optima red top, alternators were brand-new when installed.

I do like your idea of running a ground from the battery to the compressor directly. I will definitely try that.

If it's not a ground, why else would the compressor cause such an electrical disturbance when releasing the clutch?

I'm confused- You first said 'the problem is only pronounced when the AC compressor is engaged'. Here, when 'releasing the clutch' (or when disengaged). The clutch is relatively low power, so I doubt its the problem.

What kind of "disturbance"??? Depending on what you are looking at it with, you may just be seeing the the results of induction as the field in the coil collapses when it kicks off (along with the fans, relays, and maybe a bad condenser (capacitor)???
Elaborate, from the beginning, what you did to improve it, what exactly improved, what it is doing now. -- Don't worry about too much info. It's easier to ignore than guess the right question to get to "what didn't matter"

[Regulus]

-- Don't worry about too much info. It's easier to ignore than guess the right question to get to "what didn't matter"

As far as I can tell, the problem only occurs when the ac compressor disengages. The battery idiot light would come on for about a second when the AC compressor disengaged. eventually, it fried a regulator on an alternator. Another indicator that the problem occurs during AC clutch release is that I fried a Dakota digital clock in my consol when the clutch disengaged (well, on a few cycles the clock flickered on/off, then it died). After a rewired the battery ground off the frame to the transmission, the problem seemed to go away for a few cycles, but cam back after 5-6 on/off cycles. This problem exist even when set to By-level (I understand that that setting also engages the compressor). I've try two separate new alternators, with similar symptoms.

I also tried wiring in a diode inline to the compressor, but i didn't help (it was only a 6 amp diode)

Beyond this, i have no ideas.

Thanks for everyone's help thus far,

Alex.

[Ron]

Ah, I remember the problem somewhat from the old forum now...

You might try this:
Remove the wire feeding the compressor. Then run a fused wire from the battery (+) to a switch and on to the compressor. Now, place all of the controls as when calling for AC and use the switch to engage/disengage the compressor (simulating cycling). If the problem doesn't show up after doing this, say, a dozen times or so (twice what it normally takes for the problem to show up), you have probablly eliminated the compressor.... Be carefull not to run it too long at a time causing the pressure to get too high.

[dmc6960]

all the lights are LED on the car

I would just like to verify that your battery light in the instrument cluster is or is not LED?

It should not be LED.