Alternator warning light

[ianess]

what could be causing my alternator warning light to occasionally glow faintly? I`ve been using the lights and heater a lot lately.

[Jay70]

It could be that your altenator belt is loose and slipping slightly. This can often result in a screeching noise from the belt esp on a damp day if it gets too loose. It could also be the output stage of the altenator on the way out. The output stage normally consists of a retification circuit which changes the AC (altenating current) supplied via the altenator windings, to a dc (Direct Current) which is then fed back to the battery via a voltage regulator. If a doide has gone in the rectification ciruit the output from the altenator may only be half wave rectified and hence lower in average voltage. A voltage regulator maintains a fixed output voltage over a range of input voltages and may also be causing problems if it not working correctly. The best thing to do is to test the voltage across the car's battery terminals when the engine is running. Idle the engine until the output voltage is steady, the reading should be approximately 13.5 to 14.6 volts DC. Then switch on as many accessories as possible e.g. headlights, heated rear window and heater blower and check the voltage is at around 13 to 14v DC. If not then it seems likely you will need to either buy a new output stage for your altenator or but a new or recon unit. If you do buy and fit a new output stage yourself it would be worth fitting new brushes in the altenator as well. Often your old altenator can be given in exchange when buying a new or recon unit which will give you a discount on the price of a replacement unit. Hope this helps.

[Philtaz]

Also, with the onset of winter it would be a good idea to get your battery checked as it will be seeing a lot of use. Most garages do a battery check for free these days.