Voltage regulator???

Question

Ok I asked before about my battery draining when I use my A/C. A few people came up with the same answers I came up with but one person said it just might be the voltage regulator. I am beyond my witts end and desperately need help here.

Heres what happened:
When I idle with the a/c on the battery drains. This includes traffic, at stop lights, stop signs, and in park.
If I keep holding down button to close the window when it is fully closed the battery drains very quickly.
I brought it to a mechanic and he said the battery is at full voltage and so is the alternator. He mentioned the alt is around 700 - 750 when my car needs around 650... (something like that) and the bat is at 16.
The compresser is fine because while I drive the a/c kicks out majorly cold air and still kicks it out when I idle .. the bat just drains.
The belts are all fine
And he also cleaned out the fuel intake.

No solution.. I get the car back and it starts again a day later. Please help...

Answer 1

Take it back to the mechanic and have him run a load test on the battery and the alternator. You might have a dying battery, but I'd bet that it's your alternator.

When your engine is running, the battery should not drain at all. The battery is there pretty much just to start the engine. Once the engine is running, the alternator supplies all the power that you car needs; there should not be ANY drain on the battery! A bad diode in the alternator can cause this problem. The voltage will test right with little load on it but once a load is placed on it, it can't produce enough power.

Answer 2

The voltage regulator is most likely a unit housed inside the alternator. Most parts stores will test these for free. Did your mechanic load test the battery? I have seen batteries test fine but still cause problems.

Answer 3

A car at idle, the alternator can't handle loads, you have to have hight rpm for it to do so.