A follow up post to the problem I described.

I received several replies offering solutions since the post went live. One of them, from Mr Quek, a genius in my opinion, suggested I plug the board back and try again. He seemed to be confident of some loose connections causing the problem. I did try to fiddle around with the connectors the night I dismantled the circuit board. But you know what? He is right!!! That confirmed that he is indeed a genius!

Thank you, Mr Quek!

We had a terrible night on Saturday when the Aircon didn't respond to the remote control. There is only a switch to turn on or off the unit but nothing to adjust the fan speed and temperature. It was such a warm night...

The remote control works when used on the A/C in my workshop. That means that its the receiving end that is giving the problem.

After church services and dinner on Sunday, I dismantled the A/C unit enough to expose the board. Did the same to the A/C in the workshop to swap the 2 boards.

The A/C now works as it should. So my guess is correct. Next would be to figure out what's wrong with the board being swapped out. I'm guessing it is just the IR receiver. Anyone know how I can test to confirm this?