Hi everyone, my 2wd saff cossie has a volt guage fitted. Start the engine and the charge light on the dash goes out immediately(as it should). After about ten seconds the volt guage comes to life and reads 14 volts(its always been slow to react). All will be ok for about 10 minutes then the problems start! The higher you rev the less charge the volt guage reads, then it does what it feels like up and down like a yo-yo,anything from 0-14 volts as it pleases! So i thought dodgy guage,afraid not that simple.Went for a run of about 15 miles,returned home,switched off,tried to restart but not enough life in the battery(was fully charged before i set off).The battery is not very old and i dont think its the alternator as the charge light doesnt come on or even glow! Any comments or ideas will be much appreciated.

 

Without doubt the alternator at fault, nothing else could cause this.
I bet if you hooked up a dig gauge it would show this as you drove.
The warning light is a INDICATION only, it is is possible for some faults to leave a charging alternator even thought he light is on, or not charge even when the light is off, depends what part has gone, in your case the regulator rectifier, but cheap to do a recon should be about £45, as nothing special, the bist on the last one I did were £28, so for the hassle now I just let them do the work and get a year warranty.
Got to a commercial type place for best prices.
tabetha

 

cheers tabetha,i was always under the impression that if it was the regulator was the problem the charge light doesnt come on at all with your other lights before starting?

 

No even with a dicky regulator, depending on exactly where the bad joint or wahtever is can still work the light as normal.
Have had a few on the rollers that have melted the solder due to extreme heat not on cossies but on other cars!!
tabetha

 

The thing with battery lights is they are just useless. half the time even when the regulator pack fails the light still wont be on, the light can only be on if the output from the alternator is fully earthed.

Your problem sounds a lot like a car i had years ago, the light never came on and the alternator was charging, but the brushes were seriously worn and it wasnt charging at a high enough amperage, sat in traffic etc once the cooling fan came on a couple of times the car would cut out because the alternator couldnt supply the current needed.

you'll probably find your alternator is bosch and usually they are very easy to change the brush/diode pack on, costing you probably £15 - everyone seems to run out and buy a new alternator for £90+ in these circumstances, and is more often than not a waste of money.