Battery dies when car is wet?!?

[porschegrrrl]

Hi all,

My battery dies when the car gets caught in the rain (no smarty comments about not driving in the rain -- it's too late for that!!!) -- the battery discharges completely while driving the car -- and seems to be a rain-only phenomenon -- we've checked:

-- Leakage current (drain on battery with car off) is only 8 mil amps, so no grounds.

-- Alternator is charging the battery when tested in garage setting (not raining).

-- Engine compartment and battery area not getting wet.

-- Alternator belt is not slipping and is tight per Porsche specifications.

Any ideas or anyone seen this happen before?

Signed,
Damsel in distress (the car, not me)
Lila
1980 911 Targa

[feelyx]

What year is your car? I have seen older voltage regulators fill up with water and stop charging the battery.
Tim in Sac

oops!!! didn't see it under you name there

[Don Wohlfarth]

Give us more info when this happens. Does this happen every time you drive the car in the rain, never any other time? Is it always at night or are you required to run your headlights when you use the wipers? Are you by chance sometimes running the a/c (not heat) to keep the windows clear? When the alternator output was checked was it done under load or did the mechanic just check the voltage at the battery and say it was OK?
It may be the alternator is not charging the system under load or it may be a bad battery. If your battery is over 3-4 years old I'd look at that first. I've had strange electrical problems come up with a weak or faulty battery.

[porschegrrrl]

Thanks for your response!

Here's some more details.


--- The voltage reads 12.7 @ 2K RPM (with headlights on).

--- I have experiemented with this, and tried shutting down everything else -- A/C, heater, headlights, wipers -- and the car still dies.

-- Battery was replaced 4 months ago and was recently checked -- that isn't a problem either.

Thanks again for your help!
Lila