360,000 miles :)

[Fummins]

Welcome! I think you've got the highest mileage Mirage on the Forum now. The highest in the fleet I maintain has 565,000km/351,000miles.

Chances are you have a broken wire in the harness along the front top of the intake manifold. It's a relatively common problem that I found years ago on these things. The spots where the harness is zip tied wear through and eventually wear through the insulation and leave the wiring hanging on by a thread. It seems to most often do exactly as you described. Battery light on and it overcharges slightly. There are a few threads about this. I'll try to upload some pics of the places to look but basically start on the passenger side of the harness at the top of the engine where the ground to the head and alternator harness join then un-tape it, loosening off the zip ties along the harness towards the drivers side around the corner to where the harness gets chunky and the maf wires join in. Inspect it carefully, I think it's the red or white with red trace wire that tends to wear through. Usually at the zip ties closest to passenger side but sometimes closer to the drivers. If you don't see any obvious breaks, give each wire a slight tug along the entire harness. Even a pinhole in the insulation can corrode it inside.