For those of you with a voltmeter gauge, how much does your measured voltage dip (at the point of measurement) when you have the AC on whilst stationary?

Mine drops from about 14V to about 12V when the electric fan toggles on and off. This is matched with a dip in the cabin fan speed.

Measurement is taken from from the radio harness in my car.

Car is idling at about 850RPM, there are no dips if the revs are over about 1000RPM.

 

So Lovejoy,
Did you ever get a response from anyone? It is normal for these cars to do that? Just started monitoring my voltage after an alternator replacement to keep on eye on it i am seeing the same thing.
Thanks

Tom

 

My '04 R53 does the same thing......voltage comes right back up when starting out from a stop......

Bryan

 

Same here - 2002 Cooper S - 14.2V running, 12V+ up&down at idle with A/C fans on.
You're asking a lot from a relatively small engine & alternator.

 

You can have a shop that can access the ecu bump up the idle speed 50-100 rpm. Love it on mine, no low idle vibrations either.