911Jetta

Except for some "spirited" weekend drives, I haven't had much opportunity to use my car on a daily basis (I bicycle commute for many of my needs). So it wasn't a great surprise to find out that my car had a dead battery. Jump start the car and it works great for the rest of the day... then it sits for a week, jump and runs great again. It wasn't until I had the opportunity to use the car on consecutive days that I started to worry that I had a battery drain issue?! I jumper-ed the car and drove to a shop. The battery and alternator tested fine, they said it needs to be driven more... (enjoyed telling the wife that!)

So the next morning the car was dead again. There must be a current drain somewhere...

So a quick Rennlist search brought up a ton of useful information (I love Adrian S. old posts!)... just were to begin? Checked the usual culprits: hood light, engine light, glove box, sticking window switch, etc. Everything looked good. So I bought a multimeter, and decided to start testing fuses...

Then I remembered a weird situation with my interior lights...

I had them turned off, so they never activated when the doors were open. I remembered, before I manually turned them off, that there was sometimes a delay for them to come on... I would open the door and sometimes it would take a couple seconds for the light to pop on...

With the interior light set to go on with the door open, I tested the driver's door switch. Door open, door closed = light on, light off. Then on to the passenger side. Door open, door closed = light off.

I pulled the rubber cap off and manually pushed the door switch in and out with no effect on the light. Since I know nothing about electrical systems (a complete disclaimer about the advice I'm giving) I assumed a light not working meant no battery power needed, so no battery drain?

I was wrong. I unscrewed the door light switch and pulled it out of the door frame. When the very end of the wire (attached to the door light switch) contacted the bare metal of the door frame, the light came on for the first time... So I carefully screwed the door light switch back into the frame and now the lights turn on and off with the door being opened and closed.

So the next day (after a time period that would have normally left me with a dead battery), I open the driver's side door, light pops on, car starts fine. Started again this morning (30+ hours later). Problem solved... now I look to make sure the lights come on every time I open the doors...

Other random bits to those diagnosing a similar problem:
-In searching for the cause of the drain I also came across this bit of information that confirmed that my circuit was "earthed" (meaning ON), my electric windows worked with the door open and the key out of the ignition. This meaning things were still "active" and the circuit is slowly draining the battery.

-To prevent battery drain problems, some on this board have taken bulbs out (trunk, engine, glove box, interior)... does this really solve anything? My interior lights were turned off, so my battery drain problem was never due to the fact that a visible light was causing the drain. Even though the light was turned off, it was still "earthed" and causing a drain... wouldn't removing bulbs (instead of leaving everything active) leave you without any kind of warning?

groovzilla

it wouldn't be a bad idea to replace your switches...they go bad after time and you may have the same issue again if you don't replace the switches...

mine worked fine for a few months then gave me battery drain problems so i replaced them and never a problem again.

911Jetta

William,
I think you're right. The main thing is that I now know what to lookout for.
BTW, your previous tread/posts on this subject were very helpful!
Thanks, Udo

groovzilla

glad the posts helped...

elbeee964

huh! - a couple more of those 'used-on-every-911-since-1964' part numbers...

jimq

I had a battery drain problem when one of my heater solenoids decided to quit working.The battery would die over night.

CS Mende

A quick +1 and thanks to all in this thread -- I noticed after a few days the battery cranking seems a bit weak. Tested and bingo -- windows still work with the driver door still open, but don't with the pass door open.

While I'm here, what's the trick for replacing a bulb inside the dome lights? I don't want to snap anything trying to pry the cover off ...

dan79brooklyn

Many battery drains (mine included) lead to problems in the interior/trunk/engine compartment circuit.
Often it is in the door plungers (though in my case it was the engine compartment light that was shorting out and blowing the fuse). It took several trips to the mechanic to solve - unfortunately.

Michael D'Silva

great thread.
I'm bringing it alive again, since I think it has helped me source and fix my battery drain issue.
The interior lights would only turn on when opening the passenger door.
Also, the windows would still work too.
Only if I opened the passenger door, would the p/windows stop working.

I haven't replaced my switch yet, but after working it a bit, it seems to be OK.. i will monitor and see if I have found the source of my woes.

vagluv

This may help here if someone is trying to track down an interior lights issue. Check that the contact for the frunk light switch is lining up and making contact. For some reason mine wasn't, and was causing the interior lights to stay on. A quick adjustment and all was perfect.