Hey guys! Been away for a long time but I'm back and want to get the 964 in the best shape possible

After 2 years my battery was showing it's age so I got a new one. Plugged it in, drove round the block and was happy. 10 days later I come and the battery is totally dead. So I realised there is some consumer and decided to unplug the trunk light that wasn't working anyway. I tried to jumpstart the battery, but even after almost 10 minutes charging it could only barely crank once slowly.

Since the battery was on warranty I took it back and they charged it up, telling me I probably had a problem with my car's electrical system. I plug the battery in and the dashboard lights up. I hold my breath, turn the key... and... nothing! everything goes black in an instant. Totally dead!

Do you think a major fuse is blown? I am close to getting the recovery truck but I would rather solve the issue on my own if it isn't too serious.

Just a note: my cruise control fuse keeps blowing out, so I'm guessing there is some moderate electrical issues that need attention here

 

If the battery has been left in a heavily depleated state it may well be toast!
This can damage the battery and its ability to hold a charge.

 

Do you have access to a multi-meter? Can you measure the battery voltage? It should be at 12.5 volts if fully charged. If its less than that, try charging again and measure the voltage. If its not holding a charge then you need another battery. If its holding a charge and the car isn't starting, check your ground straps at the battery and starter. The best way is to remove them, clean them thoroughly and reconnect. Corrosion over time can increase the resistance.

Once you have a good battery connection, your starter should work. If not, you may need to remove the starter to have it tested.

As for the cause of the battery going flat while parked, the process of finding the cause is not difficult, just tedious. You hook up your multi-meter set in DC amps in series with the battery. Be sure that all interior and trunk lights are off. With the key off, start measuring the current draw. A normal 964 should have between 40-60 milliamps of current draw. If yours is higher, then start pulling fuses, one at a time until you find the one that is causing the problem. Then consult the electrical schematics to see what is on that circuit.

About 3 years ago, I had had to go through this process. I had a 500 milliamp draw. The cause was a faulty CCU. It took me about a full Saturday to track down the problem.

Good luck with the repair and let us know if you need anything else.

 

As above there could be loads of reasons. When mine did it it was the boot/bonnet lights were staying on as the switch was faulty.

 

Could you just remove the bulb, or would the fault continue until you replaced the switch?

Chris

 

As a short term fix, you could remove the bulb or disconnect the connector going to the trunk lid. Either would stop the excess current draw.

 

Thanks Rob

Chris

 

..

 

Yep just removed the bulb until I had the switch replaced. Initially thought it was the battery as well so was replaced by euro car parts under warranty.

 

I had this problem, brand new Bosch battery flat in a week.

I did a little digging and found 2 immobilisers, 1.5 alarm systems and the reminiscence of an 80's mobile phone system!!

Amazing what you can fit in all the nooks and crannys.

Pulled out the obvious and left the immobilisers.

Still runs flat when its left over the winter.

Eventually when I get it re-trimmed I am going to attack the wiring get rid of all the rubbish.

Good luck

 

Mine now lives on an accumate just in case. But it has been left for some decent periods and still started so it's sorted as far as I'm aware.

 

On my car the glove box lamp switch failed closed and would flatten the battery. Deactivated it.

 

If you are putting the car in storage, you need to either disconnect the battery or use a battery maintainer. The basic current drain will flatten a battery in a month.