Just an update on this one. The alternator light is on almost constantly now despite driving 600kms a week without any problems.

There must be some problem with the wiring to the light though I am not sure what it could be.

If the alternator is working but the light is on, must be a fault in the lighting or sense circuit. Either you have an open circuit sense wire (Y-W) or a short in the lighting wire/circuit (GY-W). Both these wires connect to the side of the Mitsubishi alternator. First get a multimeter and switch to dc volts (20V range). Switch the ignition on and check for battery voltage at the sense pin (at the 2 pin plug rear of alternator. Between the Y-W wire and clean chassis point). If you don't have battery voltage between this pin and the chassis, you most likely have a bad connection at the plug (side of alt) or corrosion/open circuit wiring. If you do have battery voltage, turn ign off, remove 2 pin plug from side of alt and switch ign on. If the light is on, you have a short in the lighting circuit (grey wire with white trace).

My light kept flickering as well turn out to be the earth wire that bolts onto the block near the alternator it was very loose tighten it up and no problems now

Yeh Alan. Had the same thought originally. I already asked rallyboy77 to check that in my original reply.

Thanks alfy12. I'll check the wiring as you describe on the weekend.