I would say is wiring problem or short circuit. you will need wiring diagram, voltmeter, and lots of time to find fault.
But when the battery lamp comes on when driving it may be your alternator, which is electric generator that keeps battery topped up with power. to check this you need to measure the volts coming into battery. should be 12 or 24 i think depending on vehicle. but it may be something like 11.3 or something.
test your battery between the 2 contacts when engine not running, then start and check again. go for long drive and measure again both running and not. you should get near enough the same readings within a few %, but if you are getting less the more you drive then it may be your alternator. If you are getting same readings then it must be wiring or short circuit.
i would just ignore it. but maybe monitor battery power once a week or so.
Liam, September 2009
