My (Carrier) thermostat was on E3 when I returned from work this afternoon (6 p.m.)
I reset breakers for heat pump and for furnace, changed filter and then my son opened the back of the thermostat - closed it back up.
Now the thermostat screen is blank and there is no airconditioning, no fan.
It is a duel fuel system.
What is wrong and what else should I try before calling in a repair service call?