CONFOUNDING electrical issue ~!
 

Hi All,

sorry for the length of this post -

I just got my 1991 oak green metallic 964 back after about 18 months in storage / having a bunch of work done. The motor was rebuilt after pulling 3 head studs, so after much debate, i took the "opportunity" to have the bottom end done as well. The still original suspension was shot, so it also now has new bilstein HDs and H&R springs. The car drives like a dream and its wonderful to have it back. Except.........

it now drains the battery in about 3 hours when switched off. Thats a huge draw on the battery, should be easy to sort out - right ? Ugh. Wrong so far.

I took my ampmeter out and got to work, pulling all the fuses and relays on the front fuse box (many times) while the meter was connected in serial to negative terminal of the battery. No go. huge draw still there. Getting to the edge of my ability, i took it back to the shop. We checked the stereo, disconnected the motor, pulled every fuse 2 times, and generally played with everything we could. no luck.

A few years back, farnbacher loles replaces the starter motor, crimped something - and there was a similar problem. Eventually they figured out that a wire was rubbing the cradle that holds the starter and it was causing a short. I thought by "disconnecting" the motor on the two large pin connectors in the back of the car that would have stopped the drain if it was starter related, but the drain was still there - so i am semi confident that is not causing this issue.

I missed the car for so long, and it was so $$$ to fix, that I want to drive it this summer, so I have rigged up a kill switch and i just turn it off when i am not using it, but this is just killing me.

So - after reading through all the electrical relates posts, guys i promise you - this is not related to any interior lights (glovebox or otherwise), and i have gone through every singles fuse many many times. The car does not have a secondary amplifier, and the stereo is not the source of the drain.

IMHHHHO .... it seems like the drain needs to be coming from something that is "hardwired" to the battery outside of the fuses.

Has anyone had a similar experience / what would you try next if you were me?

as always, thank you for the help - and picture of the car included !

This might be the obvious thing to check, but how old is the battery? Same one you had in the car before storage?

Disconnect the CCU and try again?

Thank you for the responses - its a fresh battery, but we have not tried disconnected / re connecting the CCU - will read up on how to do that.

please keep any thoughts / ideas coming.

The alternator itself can actually cause a drain. Sounds like you've gone through most of the other possibilities. Pull the wires on the alt and see what happens with the ammeter.

Looks like a beauty. How many miles?

Thats a great idea on the alternator - will try that - but wouldnt that drain have shown itself when i disconnected the motor from the power plugs in the back ? or is it wired separately ? either way - will check - thank you.

84k miles

Also check the alternator cables. Maybe one is chafed.

How many amps are flowing with everything shut down? If it drains the battery in 3 hours it must be 10 to 20 amps. If your amp meter shows a lot less than that, your battery is not getting a full charge. I'm sure you know that deep discharges are very hard on car batteries. It usually takes several days at 2 amps charging to recharge a severely discharged battery. It is best to remove the battery from the car and not to charge it at a higher rate than one to two amps.

If it really is discharging at 10 or more amps, I would strongly suspect that the alternator is the problem.

As mentioned above, the CCU can develop a fault that prevents it from shutting down. However, this will cause a current draw of about 0,5A, and is fused by Fuse 1.
You must have a lot more draw than 0,5A. I would also suspect the alternator diode bridge/regulator to be the culprit here. The internal diodes may be damaged.
Cheers,
Tore

can't offer any solutions here, but subscribing for future reference...

Think Rocket Rob has a good point. I had similiar issue and found that it was a worn cable going to the starter. It is a long cable and over the years can wear in spots. Mine had actually burned a hole in the sheet metal. Considered myself luck to have caught earl.

SOLVED
 

Hi All -

I finally got to the bottom of the issue, I wanted to post it in case anyone else has this problem.

The large draw was coming from two places:

First, there was a wire which had burned / been worn over the years and it was in contact directly with the starter. I believe the wire has something do with heating controls but im unsure. That was half the draw.

Second, the ground strap had been replaced with an incorrect part - that was the other half.

Thank god.

Happy new year and thanks for all the help.

Glad you found worn wire - just points out at the age of our cars and miles driven, worn cables and aging rubber is becoming and issue - a lot of these areas should be replaced for safety - ie. fuel lines for one - major electrical lines another, inspect and verify -

A clamp on current meter is very helpful. With that kind of draw you can quickly identify which wire bundle is drawing current, and narrow from there. Also with that much draw you will be producing a lot of heat. Rent a flir camera, let the car sit in a cold garage to cool overnight, flip the switch and scan around, under and in the car for for a heat plume....