how do you no the alternator has gone on a vectra

stan, July 2011

the light comes on and the battery goes flat.
If you want to diy test it you could try aiming the car headlights at a wall on a dark night and see if they get brighter when engine is revved or use a multimeter on the battery and monitor the voltage with the engine stopped and then with the engine running.Volts when engine is running should be higher

Steve, July 2011