Reverse Cycle A/C operation

Hi guys,

I have a 2 horse split system that is acting up. It works perfectly on the cooling cycle, but won't do anything when switched to Heat - which is what we want from it right now!...

I have metered the signals between the indoor and outdoor units, and suspect a failure of the indoor control board.

There are 3 x 240v control connections between the two, plus the main power to the outdoor unit. In cooling mode, the outdoor unit receives 240v signals to turn on the compressor and the blower fan, but not the solenoid. In heating mode, it doesn't receive any 240v signals at all. I'm guessing it should receive all 3 - ie compressor, blower, and solenoid. My assumption is that the solenoid is responsible for reversing the flow of gas, thereby reversing the cycle to heat rather than cool.

I have electrical / electronic qualifications, but refrigeration is deep black magic...

If I'm on the right track, then a replacement control board should fix my problem - if not, then I'm hoping there is some wisdom here that may light my path.

Yours in anticipation,

Pcal


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