alternator light

[Mike Usiskin]

Hi all,

I 've noticed that when my car is idleing at about 1000rpm (down to about 800pm when really warm ) the alternator light glows red ( ok so I don't expect it glow any other colour ). As the revs rise the light goes out. Whats going on? Does this mean I need to look at my alternator or some other untold malady ?

regards

mike

[chris68]

Hi Mike,

It means your alternator output voltage is below your battery voltage and hence your battery isn't being charged. Normally with the engine running, the voltage measured across the battery should be about 14V due to the charging effect of the alternator. A regulator acts to maintain a constant output voltage from the alternator irregardless of engine speed.

The problem could be with the alternator, regulator or maybe just a slipping drive belt.

Cheers,
Chris

[butzsi]

Mike , it can also be caused by voltage drop in 30+ year old wiring connections. Check the voltage at 2000 rpm with the headlights and
heated rear screen on and you should be seeing 13.5 - 14.5 volts. If not then start looking at voltage reg etc but if ok I would suggest checking/cleaning all connections starting with battery earth lead to body connection and working back from there.

Chris