It hangs up in the defrost Cycle when it gets really cold out, causing only the Heat Strips and the Air Handler to recycle the indoor air which doesn't provide much Heat. If i bump the thermostat down causing everything to shut off, for a couple of minutes and then bump thermostat up enough to call for Heat everything comes on and works fine the rest of the day and night until it gets reall Cold out, then the same thing happens again, with the cond.unit hung up in the defrost cycle, the cond. only Humms and the fan doesn't run, what might the problem be?

Heating & Cooling - Weather King - 10AJA4201AH Air Conditioner