Charge light coming on at high revs

[craig_tvr]

On Friday the charge light came on on the dash of my '94 4lt chimaera. The light only comes on when the revs rise above approx 3000rpm, and goes out again when the revs drop below that. Any ideas?
Thanks.

[GreenV8S]

Wierd, can't think of any obvious explanation so my best guess would be the rectifier pack in the alternator starting to break down. Could also be caused by a wiring fault but I'm struggling to see why this would be rev dependant.

[the dodger]

Belt could be slipping at higher rpm?

[GreenV8S]

Its a thought - worth checking the fan belt tension.

[spend]

I see something similar, after looking into it:

Ignition circuit reading 14v, alternator sense 12v, just enough to faintly light the LED (can only see it faintly at night).

Turning the heater fan on full reduces the ignition voltage to 13v & Led goes off.

So is it a case of the wromg LED fitted, or a fault in the alternator?

Dave

[julianhj]

Had this one!

It's your alternator in the early stages of failure. Mine started to come on at 5k, then came on progressively lower. Took around 3 months to pack up (I'd taken it to the garage to get looked at, but they couldn't find a problem with it).

If yours is coming on at 3k, you've not got long before it goes pop.