Player0

Occasionally I go out to my 86 944T and the battery is utterly dead. The battery is fairly new and the charging system is good. But something is sticking on and killing the battery. I've recently replaced the fan switch and all of the temperature switches including the one for the turbo pump. But I have only replaced the DME relay so far in this car.

What would be a good place to start? I'm guessing I should replace a few key relays. Apart from the turbo pump and the cooling fans, are there any other common battery killers on these cars?

Is there a checklist somewhere for hunting down these issues?

Thanks!

pa944red

Check the switch on the jamb that turns the interior light on and off. Do this buy turning the key off, removing the key, open your door, and see if the window switches still work. I found my switch would stick allowing the windows to work with the key out and the door open. After cleaning the junk off it and hitting it with some silicon spray, no more sticking switch and no more dead battery.

Of course YMMV.

Tom

Fractured

One other thing to check is the glove compartment light. They have a habit of staying on (it happened to my dad with his '87 951 and took awhile to discover).

CliveB

How long are you leaving the car unused? There is a small drain on these cars that will take the battery below the level required to start the car remarkably quickly, especially in the winter.
I have a low charge unit permanently connected to the cigar lighter when in the garage. A messy alternative is to disconnect the battery if you are leaving it for more than a few days.

Van

Just to clarify, Porsche designed it so after you turn off the ignition, you can still use the power windows until you open a door. There is a relay that stays "turned on" to be able to do this. If you have a faulty door switch, then the relay stays on and will drain the batter in a few days to a week.

aj986s

Also check the condition of the battery. I've been having dead battery issues with my 944S2, that I attributed to non-use. But when my '85.5 and '89 had both sat idle for about 2 weeks, and the '85.5 started right up but the '89 was dead, I decided to put a charger on the '89. Its a CTech automatic charger that changes the charging level, and I noticed that the the battery would not go above 1/2, and then heard a hissing from the battery, which was also warm. Its an Optima RedTop, dated 5/09, so I figured it had basically gotten to the end of its life. I bought a replacement, and put in on my workbench with the same charger. Quickly showed full charge, cool battery and no hissing.

Player0

Oh, well in the winter, I've only been driving it about once a week just to keep it going, but I go for about 40 miles a shot. This last time though I let it go for two weeks. I bought the battery new when I got the car in 2011, also an Optima RedTop, but honestly it's been run to completely flat a half dozen times at this point.

I didn't realize there was *always* such a drain on these batteries though. I should hook my ammeter up to the battery with the thing off next time.

Would a solar trickle charger do the trick or do I need to find a way to plug something in? This car sits outside unfortunately.

pa944red

If you are going to hook up an ampmeter I would do so on each and every circuit in the fuse box. That way you know what circuit the drain is on. But before you do that I would check the lights and switches noted above, easy things to check.

As a comparison, I could let me turbo outside in the middle of a PA winter for weeks and it would start up. The 84 I have would routinely sit for months and fire up with a jump or trickle charger.

And to answer your question, a solar trickle charger might work, but you have to determine the drain amperage to size the charger, and honestly that is only a bandaid for the issue.

Tom

Toran

I had been using a VW solar trickle charger with good results

dz302driver

I just went through tracking down this issue on a recent purchase. Battery drained in a few days. After using an ammeter between the ground cable and the negative battery terminal and finding the standby parasitic drain at about 48 ma, I pulled and replaced every fuse and relay but the drain was unchanged. I could remove one of the cables from the positive and the drain went away. I pulled the connector off of the factory alarm box and the drain dropped to 4 ma. Solution: bypass factory alarm. Good luck, it is a challenge.

Toran

Nice one dz302driver!

When you do find battery draining solutions for these cars it is a wonderful Platinum moment.

jpk

If you're only driving it weekly for maintainance, I'd suggest just disconnecting the battery. All it takes is a 13mm wrench to loosen the negative clamp and pull the cable. If you want to get fancy, you can get one of those battery disconnect switches (here's one for only 70 cents... + shipping )

75ohm

disco battery/or trickle charger, as mentioned. I have mine on a charger... no issues since.

mazdaverx7

i leave my battery disconnected when the car is parked in the garage. i have a new battery and it will be dead within a couple of days if i don't start and drive the car. i have not gotten around to diagnosing the draw. i may look into dz302driver's advice and check and bypass the factory alarm.

Funn944

6 year old Die Hard in my '86 N/A. I leave it sit for several weeks at a time. Also has flashing LED's near the door locks when it is locked. It always starts up