allenjdmb

This 964 looks like it has had a current drain issue all its life. I have most all the receipts from new, and it is eating a battery more than once a year. It has doen so since the third or fourth RO of its life. Three of four shops have given it a look, with no definitive answer. My current wrench says the car just won't go to "sleep". He thinks the amperage drain at shutoff should be around 50m amps or so, and it measures around 900. So somthing is obviously running.
Anyone else experienced this, or have a suggestion, or can you point me towards a thread? Any help is appreciated.....

c2dweller

Can't help with the cause, but I can confirm your expectation of a normal reading being about 50mA. I measured mine at about 40mA.

When I was looking around many people suggested checking the quality of the earths. Next up, start removing fuses ...

springer3

You need a new mechanic if he/she cannot locate a near-one-amp current drain. 0.1 amp might be tough to find since there are multiple items powered up during normal shutdown. Like the previous poster said, put an ammeter on the power lead from the battery, and start pulling fuses. You will soon see a big drop. If you do not, you may have a bad diode in the alternator.

Where in Georgia are you?

Earlydays

.....check the luggage and engine compartment light switches...sometimes they do not turn off properly and the light stays on, draining the battery.

Frank 993 C4S

Start with pulling the #10 fuse and then check the drain again.

Jim Michaels

Ah, back to the good 'ole days of 964 current drain posts. Sorry, but I sold my beloved RSA about 6 years ago and haven't been around the 964 forum much since.

You can go around checking everything you can think of, or do it more systematically as springer3 suggests. Often "leaks" were eventually found in the strangest places. In one case an electric window motor wouldn't shut off after the window moved into the full up position.

springer3

Some "usual suspects". Feel free to add to the list:

1) Lights (trunk, engine compartment, glove box, interior)
2) Climate control unit
3) Spoiler control unit
4) Security system
5) Alternator diodes

allenjdmb

what does the #10 fuse control?
As far as needing a new wrench, this has been a problem since thethird RO written on the car, at 9000 miles. So for 18 years and apporiximately 6 different wrneches in its life, it has stumped them all.
Any further help is appreciated....

Frank 993 C4S

The heater blowers. It seems to be a frequent culprit.

dups

in my opinion is the Climate control unit, the fan sensor don't stop ...
was inside the car can be heard if you put your ear next to the Climate control unit.
three solutions:
- replacement with a new $ $ $ $
- repair by a specialist workshop
- branch of the Climate Control Unit in after contact I made it work perfectly.

otherwise verified as the load of the alternator often shows the welds are failing and the excitation of the alternator through the watch ...
you just have to repair all the welds of the watch

darth

I'm assuming one of the mechanics would have performed the obvious diag like pulling fuses, checking for running fans etc.. A more difficult problem to track down (i.e. only because it takes time to contort one's body in order to do a visual check along every inch) is worn insulation on devices that aren't fused like the starter and alarm. Check the insulation on the wires leading to these devices especially around moving parts such as the suspension where the insulation may get worn if too close. If that doesn't uncover anything, there maybe internal shorts in any device, fused or not, requiring knowledge of what is the normal current draw.

Bill

Henry964

After fighting my battery drains for 3 years I installed a cut off Switch, every time the car won´t be drived for a couple of days I cut the battery off and voila: the battery is good as new when I return to the car I know I should find the drain but nobody could....

raspberryroadster

or a trickle charger with a shut-off feature?

OUR9II

I had a head scratcher... My central lock/unlock switch was sticking and killing the battery overnight. Not sure why pulling fuses/relays did not point to this, but when I finally spotted and fixed it, all was well again. I didn't follow up and verify if this was actually a fused circuit.

kr3678

Allen is a friend, so I'm a little familiar with this car. The car has had an aftermarket wing fitted to the rear deck and the movable spoiler removed at some point in the last 18 years. I'm not familiar with the process of swapping spoilers, but I have to wonder if the drain is from this.