Amana heat pump freezing up, multiple issues

[meekster]

I have a Amana/Goodman heat pump which is freezing up. After watching it for a few defrost cycles, I've noticed it doing a few things that would cause the problem. (1) sometimes the valve doesn't reverse at all when I test for defrost, (2) sometimes the valve reverses, but only after being in defrost mode for about a minute, even though the board is showing 24VAC, and (3) when the valve is working fine, sometimes the fan won't kick back on in normal heat mode after defrost. After the valve issues, I just assumed the solenoid or valve was bad, but considering the fan issue and the valve sometimes working fine, would this point to a bad defrost board or * By the way, filter is clean, airways are open, coolant is NOT low. I would appreciate any suggestions. Thanks!

[Freon]

You're on the right track. First let's verify the changeover valve operation at the control board. Locate where the 2 solenoid leads connect to the board. Disconnect them and measure the AC voltage at the control board. Have someone call for heat then cool and see how the board behaves. Try and measure a complete defrost cycle. If the voltages are consistently good, a steady 24 volts, at the board then the valve becomes suspect. Make sure you see a steady 24 volts since a flaky transformer may intermittently be dropping the voltage causing the control board to look sick. Check all wiring around the air handler.

Did you have any recent power company blackouts or strong lightning * If you suspect the board give it a very close (magnifying glass) inspection looking for cold solder joints (loose component connections to the PCB) or an signs of a fried component. The fan not consistently operating does, as you suggest, point to a control board problem. But first rule out the valve solenoid.

[meekster]

Thanks for the quick reply! I'll check the board voltages during defrost.

[meekster]

Thought I should post the ultimate solution to the problem for the benefit of - the issue was that the outdoor unit was freezing up. Upon further inspection, the reversing valve was not reversing when defrost mode started (intermittent failure, as sometimes it did actually reverse). I checked the defrost board and noted that I was getting 24VAC to the reversing valve solenoid when called for. So, I removed the solenoid and noted that one of the contacts was fouled up (looked like white chalk all over the contact). I cleaned the contact with a bit of sand-paper and reinstalled. It has been working fine ever since. I guess sometimes the smallest things can cause the biggest problems. Still celebrating that the reversing valve is good and doesn't need replaced!