voltage when starting and driving

[350]

Is it normal for the voltage gauge to creep up from 12 on starting, to about 14/15 when driving, then after a while drop back to maybe 12 or 13V? I thought it would stay around 14V if the alternator is charging?

Are the gauges reasonably accurate in general?

I've done a search but not found anything conclusive so far...

cheers
Mike

[fastbikes76]

my VXR8 does similar, during a long trip the volt gauge drops to something similar to yours and then back up to 14V.

Its always done this and has never failed to start even when sat for 4 weeks at a at time. Personally I think the three centre gauges are for something pretty to stare at and nothing more.

[jet_noise]

Could be some kind of intelligent charging to save fuel?

regards,
Jet

[pah250]

Sounds normal to me for these cars. I've seen 14 volts a few times. Some people say that the volt meters in these cars are not very accurate, but on a few occasions I have measured the voltage to the rear lights with a multi-meter and it did agree with the volt meter on the dash which fluctuated from 12v to 13.5v depending on if the engine was running or not.

Quite a few factors cause fluctuations in voltage on these cars. Two that I know of are: if the battery control module is currently charging the battery, it will increase the voltage. Also, if the lights are on while the car is running, the voltage is also increased. There may be other factors too.

Try driving the car in daylight with the lights off and note what voltage is displayed, then put your lights on and you'll notice the voltage increases slightly.

[350]

ok thanks, so it sounds like something normal in the way the battery is being charged/maintained, that's a relief.
I'll stick a multimeter on the battery at some point and vary the load, see what happens.

[FizzysCar]

I was looking to replace the alternator on my '04 monaro, but could only find ones for the LS2/6.0L. These have a "clutch" on them and won't fit apparently. Thankfully my alternator turned out to be fine.

I suspect that if the battery is healthy it uses this clutch to disengage the alternator to lower the draw on the engine (by a small amount) - could be why the voltage varies when running?

My voltage gauge packed in a while ago and got a cheapy replacement. Reads 12v with ignition on and about 14v when engine running and driving, which are the general levels on most cars.