Vectra cdti codes

[buttman]

Hi on my 2007 Vectra cdti 1.9 16 valve was driving along and battery light came on , car is running ok so checked codes and came up with P0621 generator lamp control circuit malfunction could it be alternator , checked battery and without engine running was 12.5 volts started engine and went up to 13.5 volts revved engine and voltage stayed same put lights and heater on and still stayed the same could it be alternator

[GreenV8S]

The tests you've done show that the alternator is charging OK. The fault message you mentioned seems to indicate a fault in the no-charge warning lamp circuit rather than the alternator itself. I don't know how that lamp is driven on your car, but typically in my experience there is a 12v ignition switched connection via the no-charge warning lamp to the alternator which powers the lamp when there is a voltage difference between the switched ignition and the alternator output. The fact you're getting a fault code with this suggests there may be something a bit cleverer going on here.

[Mikey G]

On modern cars the alternator light can be controlled in different ways, either via the intrument panel and a signal from the ECU, or via the body control module, not sure on Vauxhalls as I try to avoid them as much as I can. Good luck.