I have a central air conditioning and heating system, theres 2 different systems one for upstairs and one for the lower level and basement. the one for the lower level and basement im having problems with. For the first week over night when it gets real cold it will blow all night and coolish come to find out there was frost all over the unit outside and on the condensor and the fan sounded like it was trying to turn but wasn't so i thought hey the defroster is bad. I turn the unit heat off for awhile and then kick it back on and works fine. Well today the thermostat power is off and it doesn't work at all. Can it just be a bad thermostat? Does a thermostat control the defroster for the unit outside?? Someone please help im tired of freezing me and my kids butts off.