Does your voltmeter fluctuate between 13V and 14V or is it pretty solid? I've changed my battery and now with lights and air-con on it actually fluctuates between 13V and 14V whilst idling. Once I am driving (above 1.5K revs) it goes to 13.8V and stays there. I don't remember my voltmeter doing this before. Belt seems ok and I've changed the voltage regulator few years ago. Will check the actual voltage and grounds unless yours move too! Thanks.

 

Battery 12.4V (new). It seems alternator is ok. 14.08V engine running only and 13.8V with lights and AC on. This about right? My next thought is my drive belt slipping. Changed 37K miles ago. Anyone knows what is the change interval on those?

 

While the battery may be new at 12.4V is not at 100%, but around 80%.

The different voltage levels you are observing is roughly normal behavior. I say "roughly" because the volt meter is not a precise instrument.

With no other electrical loads (other than the normal ones from a running engine) the voltage reading will be higher than when you turn on the lights, or the A/C. (The A/C is a pretty big electrical load as the A/C compressor clutch is energized - it is electro-magnetic -- the radiator fans are turned on, and the cabin vent fan is turned on.)

So your "about right" is about right.

Only time the belt slips in my experience is after a wash or after leaving the car sit out in the rain.

In these cases the voltage level reads quite low -- less than 12V IIRC -- and as the engine runs I can hear the belt give off a faint chirp every once in a while as the pulleys and belt shed water.

If the belt were slipping dry you'd know it I think as the belt would shortly fail from the heat/stress of the slipping.

 

I think it's my alternator again because when I am driving it's solid at 13.8V. Lights & air-con on - and the dial doesn't really move much: -/+0.1V or -/+0.2V. But when I am idling out of a blue it just drops for a whole 1V to 13 (goes erratic for a second or two) then returns back to normal @ 13.8V. I think this was the case before I reconditioned my alternator first time round, it was just jumping more. I guess these are initial stages and only manifest once the engine rpm's are low... Just a thought. Will observe and report back.

 

Thanks mate.

I was under impression new car batteries should be at around 12.6V? I guess your 80% refers to 11.9V being 0%? Also, as I've shut the car off the fans came on for a minute or so. I guess that would knock it down to 12.4V.

 

normal variances. i get 14 solid after a cpl days of trickle charging then settles down to 13.8.

we are all hypochondriacs about these cars lol

 

mine does the exact same thing after my alternator change. I used a new one, but it was a cheapy. Just figured the voltage regulator wasn't the best.