My a/c unit is a 2 ton Amana which supplies cool and heat when necessary. With the recent cold snap, heat was required and it was working. Turned the whole system off when the outside temp was livable w/o anything. That evening, turned the heat on and it kept blowing but with minimal heat output. Turned the a/c off again. Tested cool in the morning and it was good. What is going on with the heating element? Is it the coil or the thermostat?