vauxhall cavalier mk3
ecotech cat abs elec windows aircon....
despite engine running and battery receiving a charge the ignition light remains on...the brightness of the lamp depends on the power used by the car...eg,,if i was to press in the cigarette lighter then the ignition lamp would go bright red....yet if i turn it off then it goes back to a dull glow. simularly if i turn the cars headlights on then the ignition lamp is bright again...all this despite the battery receiving a charge..this problem has been in effect for over 2 months now and the battery has never failed to start the car...fan belt is tight....no obvious defects......im at a loss...!!...any idea's..??

Ian T, October 2007

Possibilities:

Most likely: Faulty field diode in alternator.

Or: Wiring fault between ignition switch and alternator usually caused by poor fitting of accessories into the harness.

Either fault will usually allow the alternator to charge the battery normally. The problem is that in the event of the alternator drive belt snapping you wouldn't take any notice as the warning light is already on.

So: either put some tape over the warning lamp to stop it blinding you at night and check the alternator drive belt regularly or try to locate the cause of the problem.

Dann, October 2007