964 battery issues

[rwinebrenner]

My battery constantly goes dead I put a slow trickle charger on it sine I drive it very little Today after disconnecting the charger it would not start A weak cranking occurred so I humped started it and drove it for over 100 miles When I turned it off and attempted to resart Too weak to restart again Battery is only 1yr old What should I be looking for as a problem

[Justin@Athens]

alternator not charging.

Use a multimeter on the battery with the car idling you should be getting 13v+, if not you probably have a bad voltage regulator on the backside of the alternator.

[Jim Richards]

The 964 climate control unit (CCU) has a transistor that tends to fail, leading to a small fan on the unit to keep running after the car is turned off. Actually, it's supposed to run from some number of minutes after the car shuts off, but the transistor failing lets it run continuously. This is one of the limited number of electric bugs that run down the battery on 964s. I used a DC clamp on ammeter from Sears to verify that the CCU was the source of my battery drain. When I pulled the fuse that powered it, the current dropped to a negligible amount. I looked on Rennlist for the thread about repairing the CCU, and bought a new transistor, soldered it in, and verified that the CCU no longer caused a significant drain on my battery, I hope this helps. Good hunting!

[rwinebrenner]

Since I drove the car over 100 miles after jump starting and then it still wouldn't start it sounds like the voltage regulator could be the issue

[964TargaC2]

My parasitic drain turned out to be drivers door light switch, if it isnt working power window system stays energized and drains battery, If working when you open door the power window system is shut off

It can be intermittent but easy to check, if you shut off car and open door and windows work its more than likely the switch

[MrScott]

+1 on multimeter. My guess is parasitic drain has discharged your battery one too many times and now it won't take a charge. You should get some compensation from the warranty/exchange.

[Dads gift]

I have the same issue with CCU fan running continiously and battery running down. However, if I pull fuse and then replace it, the fan stops running. Is this a bad transistor or something else?

[dicklague]

always suspect the battery first. Have it load tested to see if it is holding charge. Does not matter if it is a year old. Batteries are a very weak link in the system.

You have to eliminate the battery as a possible cause first before you start throwing parts at ti.