Battery Warning Light

[flip]

Hi,anybody. my c3 battery warning light came on after about 3 miles...and stayed on until i stopped. i went shopping and when i started the car up to make my way home it was ok unil i got nearly home and i came back on again....the battery seemed ok..any ideas anyone......cheers..

[iannez]

battery light comes on when the battery voltage drops below 10 volts. i am 99% sure it will be an alternator fault but should be checked first. some times this fault can be intermittent so car will need to be driven while tested. use the cig lighter socket to do this.

[Guest C1millstone]

I had an 04 reg C3 desire 1.4 hdi.My C3 cooked it's alternator,so badly the Dealer couldn't autopsy what was left!!!.Keep an eye on it,I found out by spitting on it the steam gave away how HOT it was!!.C1millstone.

[stimulator]

The waning light shows that the battery is discharging.

 

Under normal conditions thatw ill only happen when the engine is running BUT the alternator is not producing a voiltage above that of the battery.

 

Common cause of this is the diode pack in the alternator, it's an AC (alternating Current generating device) and the diodes change the 3 phases to a DC for the car. The old type system was a generator that was a DC machine, hoever they were inefficient at low revs. An alternator will produce above 12V at engine idel where a generator wont. So in amodern car the red light is usually only seen when the ignition is first switched ON, OR in this case when there is a problem.

 

needs a trip to an auto electrician, diode packs are replaceable but depending on age a new alternator or exchange may be a better bet. Has the old one become contaminated by engine or power steering oil?