Gus

Need some help -First, I know this subject has been covered - but I am hopping that someone that has done the fuse test/chase - like I did found a solution to my problem - SO PLEASE READ ON -
Noticed that I had a battery drain when developed a flat battery after driving to work - car started fine in AM drove to work and 4 hrs later the battery was dead - jumped and drove home ( Up to this point had not had any problems with car or battery ) - charged battery - started and drove to work / disconnected battery and then reconnected when I drove home - started - no problem - let car sit over night - dead battery - Have traced every fuse with an AMP meter and can find only a small drain at the clock (fuse #11) and at the radio (fuse #38) - noticed a larger drain at the blower motor (fuse #1) - but it does not account for the larger drain that I am reading off of the AMP meter -
I am showing a drain of 4 + amps from an AMP meter when connected to the car. None of the fuses or relays I have checked reflect this amount. With the battery out of the car and a charger connected to the cars battery terminals, with the ignition off (key in off position) I am showing a draw of 4+ amps by the car. I have disconnected just about everything, trying to find the cause and have not been able to locate the drain. I have disconnected the DME, all engine electrical, pulled the AC/heater control out/ radio is out/ have NOT disconnected the 3 units under the passenger seat.
At this point I am getting ready to go into the cab top to see if there is a short in that the motors -
If any one has done the trace for a like problem - what did you find as your problem/issue -
What tricks are there out there to try and identify the drain - ANY ONE????
Right now the most of the cars electronics are on my garage floor - and I am still showing a 4 AMP drain - or with the charger connected to the battery terminal s on the car it is pulling 4 AMPS ( IGN OFF) This should be almost "0"
say for the clock - Or am I off base and need to look at a simpler way to fix this - THks

HELPPPPPPPPP

Rocket Rob

I recently had a high current draw of 440 milliamps. As I was trying to isolate the source, I thought I had found the fuse #1 as the primary source. The following weekend, I started to continue to trace it but the draw as 1.5+ amps. Ouch! After much head scratching, it turned out that I had forgotten to disconnect the trunk light. As soon as I did, the current draw went back to the 440 baseline.

My advice is to check the front and rear trunk lights. They pull quite a bit of power and are not obvious when they are on.

Do you have a factory electrical diagram? I found that to be very helpful.

ezinternet

A long long time ago in a 964 galaxy far away (Porschephile) .... it was found that a sticky (retracted, not springing back) door switch would keep the car lighting system energized forever. By design, the system detects when you turn off the car and exit by having the door switch plunger pop out. If the plunger under the rubber boots are sticky or stuck then the electrical system is convinced that you never left the car. Battery would quickly run down.

So check the plungers on both doors, under the rubber boots, between the hinges on the forward frame (lower A pillar).

Gus

Rob - have the lights boot disconnected so that is not the issue - still looking - tomorrow will check starter and 2nd battery cable to rear of car -
EZ - thanks, will check the door switches - good idea -
found one good thread - close to issue I am having - guy said that he spent 8 hrs looking - then decided to take it to a shop - on the way something changed because when he got to the shop the issue was gone -
go figure -

springer3

Battery drain that fast could be a bad diode in the alternator. I don't think there is a pull-out fuse to isolate that.

J richard

Gus,

I don't know what your process is for running down each circut, I found the easiest thing to do is take the negative lead off the battery, and jump your ampmeter between the battery and the terminal, take a fuse puller and pull each fuse if you get one with a voltage drop keep it pulled and keep going, no drop, put it back and keep going until you've gone through them all. If you still have a voltage draw, pull each relay and look for a voltage drop just like the fuses. This whole process can be done in half an hour and pretty much isolate which circuts you are dealing with.

I found that the radio power booster circut is a common issue, it gets used for a variety of aftermarket things that may or may not still be on the car, also check the radio anti tamper switch, I found both causing a problem, I found a 3 amp draw on the radio booster, I think it runs under the passenger seat, if you get any water in the car I think it can ground this circut. And I don't mean to sound condesending, but when you have the hood or rear deck open those circuts are made unless you pull the bulb or disconnect the switch...

If its something that isn't going through the fuse/relay panel, then the only other things I could think of would be to pull the two small leads on the positive battery connection to see if you get a drop, that should isolate the alt/ignition circut and the ac fuses under the panel in the engine bay. Other than that I would be guessing, power window switch? door contact? but most of these would be fused.

anyway good luck with it thats one of the biggest PITA things to chase down on a 964....

dutchcrunch

i have done this test too and my current draw fall below the stated amount in the 964 white book by adrian, for got the name.

i can tell you that just removing the light bulb from the engine lid is not enough,
even with the bulb removed , if you leave the the deck lid open there is a high draw on the battery, close the lid and its gone. i think the central informer circuit is a high drawing system. that switch does more than just turn on and off the light!

Gus

J richard - thanks - did something similar- made a fuse insert that had to contact points on which connected directly to the AMP meter for a reading from each fuse location. As I pulled fuses and inserted my home made test fuse I got a reading for that fuse - kind of like your suggestion - THANKS-
Right now am going to check alternator and starter motor today- then probably pull fuse box and check circuits under there -
Thanks all for the feedback -

apyip

I had a similar problem last month. As it turned out, the light switch in the trunk was not coming in contact with the metal plate that was suppose to cut the switch off when the trunk closes. I disconnected the trunk light and everything is fine now. Bought an Osram LED tap light and kept it in the trunk from now on.

Gus

OK - HAve isolated the problem - But don't understand issue now - I had a 10 AMP draw - on the cable going to the starter motor and alternator - I disconnected the heavy black wire from the battery that connects to the starter and found that this wire also went up to the alternator via a heavy red wire - so disconnecting this cable removed the connectivity to both the starter and the alternator. Then checked for battery drain - there was none - so the problem is either in the starter or the alternator -
Both worked find - no issues on starting the car or with the battery charging up after it first went dead -
NOW HERE IS THE KICKER - I first reconnected the starter - NO DRAIN - then I just connected the alternator - NO DRAIN - ???????????
I have now reconnected everything as it was - NO DRAIN -
What in the starter or the alternator would cause a drain that when the power was removed would go back to a open circuit - something is sticking or starting to fail (MAYBE)
Anyone have any ideas -????????

68CGPlt

Gus, did you have any corrosion on those leads? We just spent a week tearing apart an electrical system to a helicopter only to find out some corrosion on two fuses was causing everything to go haywire. Chances are this is a long shot and what ever you did removing those cables may have masked the problem. Good luck and hope it doesn't return.

bwoodry

My glove box light switch was faulty and the light remained on in the glove box.. I replaced the swithc and al is well now.

Good Luck

Gus

No - the to leads that connected to the starter were clean - the only corrosion that I ran across was on the battery ground cable - the short multi strand copper cable - it had just a little corrosion near the ground point - but that was it - all other contacts were clean -
I can't figure out why everything went back to normal after I disconnected the cable and then reconnected.

dutchcrunch

i think there is a switch in the voltage regulator for the altenater that sends current to the battery, its not unlatching. when you disconnected the battery it unlatched. try starting the car and see if it comes back. if it does its in the altenator circuitry.

Gus

Thanks Dutchcrunch, we thought of that - started the car drove it, shut off, restarted, the issue is no longer there. What ever the problem was with either the starter or the alternator it appears to have corrected itself. Or lies in wait for me until the next time I leave the car at the airport.
It really is very strange - my guess is that it is in the alternator - maybe with diodes - but until it comes up again I am at a loss to explain what really was wrong - a 10 hr adventure in to the mysteries of the 964 electrical system -