Im trying to fix a heat pump. I may work on 1 or 2 a year so they are definitely my weakness. Anyway, its a CoAire model number COTH-48M2Z. I replaced the defrost control board after I found I have 24 volts input but did not have 24 volts output at the board. The low pressure and high pressure switches were both closed.
With the new board installed the contactor now closes and the compressor comes on, but the fan does not. There is 120 volts going into the board at CN20 but no voltage coming out on the FAN terminal. If I bypass the board the fan comes on. Why is the 120 volts not leaving the new board? Thanks.