I have a Tempstar central air/heating syatem. Model # EBX4800A. The digital thermostat is a Braeburn 5050. The issue is that in the middle of the night the unit will be blowing cool air instead of heated air intermittently. Some times it will go weeks without a problem and then malfunction 4 days in a row. It has only happened in the middle of the night which will make it impossible for a technician to diagnose. All I have to do is swith the thermostat switch off and then immediately turn it back to heat and warm air is coming back on. The heater is electric. I am not sure if this is a heater failure or a thermostat failure. Im tired of waking up in the middle of the night cold and would like to be able to give an HVAC technician the best possible chance of repairing it when I call. Thanks for your help

If your unit has a flame sensor try cleaning it. Use fine sand paper or steel wool. Open all registers and make sure the air filter is clean and the return air is not obstructed.