Mechanics

BATTERY POWER GOES DOWN WHEN I TURN

1999 Audi Station Wagon

Air Conditioning problem
1999 Audi Station Wagon 6 cyl Four Wheel Drive Automatic 110000 miles

Hello,

I have recently replaced the serpentine belt (maybe a coincidence), but since then whenever I turn on the air condition, the little battery indicator goes down from a healthy 12V to 10 V and it gets even worse in traffic jam and then the car starts vibrating and makes noise.
is this a battery or a an air condition problem and could it be due to a faulty replacement of the serpentine belt?

Thanks,

Bettina
Avatar
Bbomm
May 22, 2010.



Hi bbomm. The place to start is by using a cheap digital voltmeter to measure battery voltage while the problem is occurring. A fully charged battery should read near 12.6 volts when the engine is not running. If it is around 11.0 volts or less, there is a shorted cell and the battery must be replaced.

Next, measure battery voltage again while the engine is running. It must be between 13.75 and 14.75 volts. If it is low, suspect a generator problem.

Caradiodoc

Caradiodoc
May 22, 2010.