WTF is a Gates pulley?
Possible I suppose that Gates may put their name to a pulley, and some diesels have a freewheeling pulley that seizes, that may result in the alternator cracking its housing, but this is getting ahead of ourselves.
Battery light on is normally that the alternator is not charging. So we start there.
Possibles.
1. Belt broken.
2. Belt not tight, so slipping, normally will squeal but still give some charge.
3. Alternator failed. Should charge at around 14v with engine just above tickover. But try option 4 first.
4. Earth cable from engine to battery broken, poor connection, or not connected. Quite possible, as this is attached to the gearbox casing, so would be disturbed when gearbox removed. With clutch just done, this is probably first thing to check.
From battery, follow negative cable from battery. It should go to the body of the car, often not far from battery, but below it so awkward to see/feel. Ensure it is connected. Then same cable should go on to connect to a gearbox mounting bolt. You will probably find it hanging loose.
Battery will need recharging and cable refitting.
You can do this yourself, if you are competent. Or, if this is what you find, get repairer to recover car, fit cable properly and charge the battery. Insist that you want the battery trickle charged, not boosted. A boost will shorten its life.
