Low volt when A/C is on

[cedalice]

Hello

Since the last week I have a problem with A/C.
When I switch on the A/C, air is cold but the volt gauge is low and finally battery is off. It's the same thing when I drive.
I don't understand where is the problem ?
cedric

[gbrtng]

Originally Posted by cedalice

Hello

Since the last week I have a problem with A/C.
When I switch on the A/C, air is cold but the volt gauge is low and finally battery is off. It's the same thing when I drive.
I don't understand where is the problem ?
cedric

Measure the battery terminal voltage with an accurate digital voltmeter with and without the A/C on. With the engine idling, you should see 13.8 to 14.3 volts without A/C, and maybe up to one volt less with the A/C on. This is of course with the headlights and other electrical loads off.
If the voltage is less, you may have a bad battery or an alternator that is failing.

Not sure what you mean by "and finally battery is off".

[cedalice]

battery is off it's because it's under 8 V, the car stop.
thanks

[tccrab]

Cedric:

The problem that you have is not the A/C.
The problem is more likely your battery and maybe your alternator too.
C4's in general, and ZR1's especially, require full battery voltage to start and run.
How old is the battery?
If a you have a 5 year battery and it's 4 years old, it is time to put in a new battery
Put a new battery in it and have your charging system tested when the battery is installed.

Good luck!

TomC
"Crabs"

[Paul Workman]

Once the car is running (at normal idle speed) and the alternator is working, unless the battery is shorted, the regulator will hold the voltage to about 14.3 cold, and 13.7ish when fully charged and temp is warm. Except to "filter" ripple from the rectifier, once the engine is running, the battery does very little but sit there and be charged - the alternator carries the entire load including lights, A/C, blower motor, etc.

However, if the voltage regulator is shot, assuming the exciter voltage is present, then the battery carries the load until it becomes exhausted - which is what yours sounds like it is doing. My guess would be the alternator itself, or at least the regulator and or the rectifier within. That isn't to say the battery isn't in need of replacement, but the characteristics you describe are classic (generator) failure.

P.

[gbrtng]

Originally Posted by cedalice

battery is off it's because it's under 8 V, the car stop.
thanks

OK, that's the point where the engine control module can no longer operate - no spark or fuel injectors.

Start with checking the battery - do a load test. The next possible is the alternator is not providing enough current to run the total vehicle load - works
"OK" without AC, but the battery runs down with the AC on.