Rapid battery drain: Alternator bad??

NEWFIE 69 911E · 05-07-2009, 03:01 PM

1980 SC

My SC has a developed a rapid battery drain. Battery dies overnight unless disconnected from car. Alternator light not on when engine running.

I read some posts here, and measured current draw to be over 200 milliamp with all electrical turned off. I then pulled each fuse one and one, and the current did not change. There is quite an arc when connecting one of smaller red wires onto the positive battery terminal.

Does this mean that the alternator is bad? Should a local alternator shop with no Porsche experience be able to repair the alternator?

Safe Motoring!

dsintrepid · 05-07-2009, 04:57 PM

I had the exact same problem in my 83 cab. At one point the only thing left connected was the starter & alternator. I disconnected the starter at the battery feed (which also disconnected the alternator feed), check to make sure the draw was gone. It was gone - so I hooked up the starter only - draw gone. Hooked the alternator back up draw still gone. That was about 5 - 6 months ago & it is still going fine. When I disconnected the starter the stud turned a bit - I thought maybe it was arced to something and turning it broke the contact loose - but that seems a bit far fetched. Sorry I could not give you a definite answer. I think at that time I got a recommendation from this board to replace the alternator.

NEWFIE 69 911E · 05-07-2009, 05:22 PM

Hi Dave,

Thanks for your reply. So, in the end, you just disconnected and reconnected the starter and alternator and it has been OK since? Correct?

Seems bizarre, but worth a try I guess! I'll also check th stud on the starter.

dsintrepid · 05-07-2009, 05:35 PM

Yes - that is what I did. I did keep a jump box with me at all times for a while after that however. LOL!

NEWFIE 69 911E · 05-07-2009, 05:53 PM

Ok, thanks for the reply. I'll try it this weekend and update. If it works I will get myself a jump box

dsintrepid · 05-16-2009, 06:58 PM

Did you ever figure out what was causing your drain?

Zef · Zef's Garage

Just my 2 cents...at the next winter storage of my 84, I will remove the alternator, will send it to a shop for a complete OH. I have no problems yet, but this thing is 25 years old...A bit a proactive maintenance is sometime justified.

NEWFIE 69 911E · 05-19-2009, 06:45 AM

Quote:

Originally Posted by dsintrepid

Did you ever figure out what was causing your drain?

Thanks for the reminder.

The problem is now solved

I sorted out the wiring for the Sony CD Player. It was not correct, but making it right did not reduce the current draw; the unit still pulls over 150 mA when off. I think it has something to do with CD ejection; the unit needs some residual power stored to allow the CD to be rejected without powering the unit. Just a theory I have not had time to test yet.

So, I brought the battery to NAPA for testing; It was shot. I installed a new NAPA battery and now the car starts perfectly even when sitting for days and in the cold climate that we are subjected to here in Newfoundland!