electrical problem

[mwbaum]

Bummer...the first nice day in the Northwest all week and I went to take the Porsche out for a drive and it was totally dead. Even the alarm light and clock were stopped. No power...Zilch. All the fuses were fine and I drove it last about 2 weeks ago. I had not left the lights on. The battery was recently tested and I was told it was fine...any ideas before I call a wrench?

[mwbaum]

btw...its an 85 911

[Rick Lee]

I'm not too proficient with power issues. But there are several easy tests you could perform before paying a wrench to do so for you. Try jump starting it. If it works, get the battery good and charged and then start testing the alternator and voltage regulator. If it won't jump start, take the battery out and charge it overnight and then do those tests. It can't be too huge a deal.

[mwbaum]

Well, I tested the battery and it registered 2V, so its dead. I wonder if I have a short somewhere...it seems odd that a battery could discharge from working fine to totally dead in 2 weeks.

[Superman]

Something was using electricity during that two weeks, which killed the battery. Charge the battery overnight, then pull fuses, one by one, in darkness, to see which circuit is doing the draining. Of course, the clock is on all the time, but it does not use much juice.

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'83 SC

[john70t]

The deep-cycle batteries can take a few total discharges and maintain voltage potential under load, but not the standard lead-acid.
I wouldn't try reviving it from the dead unless its pretty new(batterys don't last more than 5 years anyways), it will probably be sufated beyond redemption, and then I'd trickle-charge it in a safe area and cross the fingers.
By the way, don't fast charge a battery in a rental unit, it may boil over and put a hole through the carpet . (I'm trying to make every mistake possible-at least once.)

You can check if there's a key-off short by putting an ampmeter across the disconnected negative battery terminal. Over half an amp and above(clock, radio, alarm,,CPU) tend to indicate a problem. Pull fuses untill it stops.

[mwbaum]

thanks...thats good info. The battery was once before discharged when my alternator went out a few months back. I bit the bullet and bought a new battery, and I'll try your test to see if I have a short