I have read various threads about electrical issues on the 964, but mine seems a little different and i am hoping someone can help solve the problem.

Car had been sitting for a while before I bought it, but always with a charged battery. I got the car home last week and after a couple of days went to start the car - nothing, flat battery. okay I thought lets charge it. After another day, another flat battery. okay time for a new battery. Installed new battery and all is well, except the fan belt snapped before I could get the car out of the drive. okay new fan belt needed. Next day went to open the car with the remote central locking fob, nothing, new battery flat!
I know the battery was good and fully charged as it was new and had seemed fine two days previously. The car had not been driven, so assuming its not alternator related, but really have no idea what could be draining the battery that quickly. before I start jumping to incorrect conclusions, does anyone have any input as to what/why this is happening. Thanks


FINALLY - I think it has been resolved

 

If you have verified the alternator is charging the battery, likely the Ccu fan not shutting off
charge battery
pull fuse for ccu
let car sit
note that ccu will run about 20 mins after car has stopped

 

Take a diagnostic approach. Set up an ampmeter to measure better drain. Ideally do this without breaking the circuit. If you do break the circuit you'll have to wait for electronics to calm down, 20 to 30 minutes.

Record your battery drain. Should be less than 50 ma. If not, start pulling fuses to identify which circuit is the source. Note, you should pull or disconnect frunk light before you do this or you'll be measuring it's drain.

Common culprits are frunk and engine light switches, door switch, glove box switch and CCU.

When I measure my cars quiescent draw it's less than 20 ma. It still drains battery in 2 weeks. I think as battery slips below some voltage that electrical Gremlins start flitting about. I would really like to put a data recorder on it.

Good luck.

Dan

 

I take it the CCU is just the standard heater control unit in a car without a/c and this too has a fan.

 

Okay, so keep Amp meter in position between Batt neg and body of car to keep circuit. I have Amp meter, what is it best to set it to to record ma. I then run through each fused circuits draw by removing each fuse in turn. Do I need to do the same with any of the relays? just want to be set up correctly before starting, thanks

 

Here's how to find any current thieves in the 964/993.
Cheers,
Tore

 

That's looks like a lot of good info. I will read and work through the suggested possible causes. Thanks

 

 

I had a 2amp+ drain that would drain the battery overnight that turned out to be the heater hose that had worn away, exposing the wires inside. The wires were shorting on something and causing a huge draw, draining the battery. The mechanic happened to see another 964 with the same problem a few years prior. Otherwise, that could have take a while to diagnose!

 

That's an interesting one. My driver side heater hose seems not to be working as no hot air to vent. Could be a cause. Thanks for the info.

 

Thanks to everyone for their tips on how to find find out where the current drain is coming from. I took a diagnostic approach as suggested and managed to track the problem to a broken luggage compartment switch. I have now dropped from around 1 amp drain down to 0.023, so I think this may solve the problem! (hopefully).

 

Worked through everything systematically, found a faulty front bonnet light (couldn't find a switch for it, on the lid or in the latch???) reading down from around 1amp to approx 0.19 - 0.23 (190Ma - 230Ma) This is still much to high, even pulled all the fuses and it remains at the stated level. Any ideas what to check next, all door switches are okay. checked the fuses in the engine compartment too. Am I missing any fuses or anything ? Fuse in radio? CCU fan is quiet, is there a secondary check for this as it seems to tally with the likely amount of drain?
Cheers

 

This is probably a stupid question but... does the current drain change when the car is locked or unlocked?

 

The switch is on the left side of the lid, near the hinge.

 

That's a good point! I have only been using the tester when the car is unlocked. Should it alter if it is locked?