Just replaced an alternator on a L reg Mitsubishi GTO, in the rain (typical) and when I'd done and drove it to the end of the street a red warning light appeared on the dash. I can't find any picture of it on Google but it looks kinda like this
( ( (
) ) )
__-----__
---___----
I'm thinking that its an alternator warning light but not quite sure what it is telling me. The light came on when I was putting the engine under a bit of load and went off when I just took it easy. It also came on with the slippery road yellow one but I think this may be a conincidence maybe as the brake pads are none existent. There was a smell of overheating or electrical like burning from the engine but I'm not sure if the belt has been slipping or it's all the water evaporating from the alternator.
Any ideas?

It could be overcharging, causing some modules in your car to throw an error.
Check the charging voltage, should be about 14.4v.
Darren

Overcharging? That'd be a regulator fault then I guess. It's the same type alternator so couldn't be that. Hmmm.

Could also be wired incorrectly?

Nah its just an earth wire with eye on the end and a keyed plug so it can't go on wrong. Its fine under a very steady load just when I tried to boot it a bit.
TBH it's had a few lights on before I started with it battery, coolant and slippy ones. Bit of a mind of its own.

My bros brand new alternator did that, the ecu light came on, that was the only indication of the charge fault.
Darren

How was it fixed?

Just found a picture of it here on a Toyota site
Exhaust Heat
Wierd why that should appear though.

[Edited on 7/12/09 by mistergrumpy]

there is a second sensor in the exhaust to warn of Cat fire/overheating
either thats failed or you have a over charging fault with the new alternator that will have the voltage reg built in

Well the owner has said that before I got my hands on it and at the start of the week the car was really sluggish and backfiring making me think that there's unburnt fuel going through and that the cats screwed.
Oh, the light means overheating cat too. Just found it.