goldminer

My battery is discharging overnight. It holds its charge if I disconnect it so I think the battery itself is OK. Something must be draining the battery but I can't see that I've left any lights on and I can't hear anything running. Does anyone have ideas? Where should I start looking?

pk951

Take a look at Clark's garage under exessive battery drain.
http://www.clarks-garage.com/

Keithr726

The switch on my door that cuts the power to the windows was bad and slowly draining my battery. How I don't know.

Tye

Probably not it since it drains overnight, but I had the problem that Keithr26 notes. If my 1987 944S sat for more than a about 10 days (and it frequently did), the battery drained to the point that it wouldn't start the car. I attributed this to the 968 motor conversion that was done by a local Porsche shop. They did a good job on the conversion, but were never able to solve this problem.

Recently I had Charlie Andrews, an excellent local 944/928 mechanic, do some work on my car. I mentioned the battery drain and he immediately diagnosed the problem. It's the switch that senses if your door is open or closed.

Here's the simple test:

Sitting in car with drivers door closed, turn key to the on position and back to off position.

Remove key.

Roll window up (or down). While window is moving, open the door.

The window should stop. If it does not, then the switch is bad - which means that a relay is always being powered - which means that your battery will drain down.

Apparently Porsche put this functionality in so that you wouldn't have to put the key back in to roll up your window if you forgot to - as long as you haven't opened the door...

(I did this from memory, so I may not have gotten the steps EXACTLY right, but you get the jist of it.) This was an easy and cheap fix, but it drove me crazy for almost a year.

goldminer

Thanks for the help. The problem has gone away but I'm not sure I've fixed it. I put a multimeter between the battery and the positive lead but every time I made the connection the alarm would go off and there wasn't enough current passing to let me switch it off. At one stage I ignored the alarm and opened the passenger door which caused the current to drop. I sprayed WD40 into the door switches, turned the alarm off and now the car is behaving. Not very scientific but at least the car starts.

VWaddict

The way to disarm the alarm is to connect the multimeter in line as a current tester, then to SHORT the two test-leads together while you disarm the alarm. -It sounds awfully like you had it in 'low current' range (high resistance) instead of high-current range... On most multimeters, you also have to insert the red probe into a DIFFERENT socket in order to read high current (usually up to 10~20Amps DC).

My Fluke 87MKIII and Fluke189 are both like that, but both of them will allow the alarm to operate normally so long as the probes are inserted in to the CURRENT sockets, and NOT the V/Ω/C sockets...

Just a thought...

Keith

VWaddict

Oh, and there are TWO sets of contacts on the driver's door pin switch, with a plastic 'rider' which runs along the switch. The second contact set is for the courtesy lamp. I too diagnosed exactly the same thing for the current drain about a year ago, and I posted a diagram of the courtesy light wiring here somewhere...

https://rennlist.com/forums/showpost...7&postcount=13

Keith

goldminer

Ahh, that makes sense. I did have the multimeter on low range. I'll have another go this weekend.