This is odd! Surprised no ones experienced this before, anyone out there? Be interesting to find the problem. Try disconnecting the battery for 5 minutes, tapping leads together and starting over?
Common on the galaxy as it has a little fuse box near battery which suffers from slightly loose wiring crimped in the terminal creating higher resistance and over heats.
The voltage here thou is too high to have a fault lamp on i would have thought.
An additional chassis earth and ideally running a cable direct from battery to alternator would be interesting
I replaced the alternator with an original OEM A2 alternator I had as a spare. The light is now off. I ordered this tool to move the tensioner a 6 point angled spanner on Amazon for £10 I put a small extent on bar in the end to get additional pull then could lock the tensioner. I’ll get the removed Alternator repaired as it looks like the regulator is faulty