I had control boards eventually fail on 3 air-cons. Same problem, fan coil unit shuts off normally, but compressor outside stays on after unit being powered off.
The first 2 they charged 2,000+ Baht each to replace. On the 3rd one they had run out of spare control boards so the guy quickly soldered it for a couple of minutes and then it was fine again and no longer needed replacing. Then charged only 500 Baht for the repair service on that one. This tells me they all probably could have been soldered and not replaced.
A nice little business they have going with control boards that all eventually tucker out, but could actually still be repaired and don't really need replacing. Hmmmm...