We bought a house two years ago with an electric HVAC system. Our last home had an oil-fired furnace with cast iron radiators (so wish we still had those) so I'm new to this type of system. We rarely use our AC - open windows and country air for the family unless it's really disgusting outside. Almost the same for heat - I have 7 cords of red oak and maple and a large wood stove that beats a 3 ton system any day of the week.

Here's the problem, the outside unit is frozen solid @ 30 degrees. I replaced the defrost board with an ICM controls so you're probably aware that there's multiple dip-switch and plug configurations.

The reason I replaced the defrost board is because the capacitor kept failing. After I began learning the new system I determined the most likely cause of the capacitor failing was due to the system short-cycling. We would sit in the family room and listen to the what I guess is the defrost cycle kicking off and on and off and on.

Although I like to figure out things on my own and have the tools to back it up, i'm not a cheapskate - I have a reputable HVAC contractor who comes out and is willing to talk me through what needs to be done and I pay him for that. The last conversation validated my suspicion that the outside unit going in and out and in and out of defrost mode with the eventual fan failing to start required a defrost board replacement.

So, maybe then I am a cheapskate because I bought an aftermarket board rather than an OEM board.

My question is regarding board ICM350 which orginally was not configured correctly in regard to switches 5 and 6. Switches 1 and 2 are both set to 'off' which means 120 minutes of defrost cycle. I powered on the system with the new configuration but the unit failed to engage into defrost. The unit is partially iced up, enough to where the thermostat should kick on.

With the unit running and everything attached / plugged in I jumped the speedup and thankfully the defrost engaged. The problem is, that lasted for about 20 minutes and then the entire unit kicked back into operation with the wall thermostat set to 68. The unit is still iced up albeit partially.

I'm ready to recall the HVAC contractor and figure this out - he's been a great help. If the Freon was insufficient I would suspect the defrost cycle would last much longer and just not do anything. If the board was bad, which I just replaced it would either do nothing or spaz out like the old one did. Maybe the frost sensor is bad?

Thanks for any feedback!