Heat Pumps and Electric Heating - heat stops working after automatic on

I have an old heat pump GE actually. one of the capacitors was replaced and also a new thermostat was installed. I'll try explaining my problem buts it hard to explain.

heat works great when iniatially turned on. but after a few times the heat turns off and on, on auto mode, warm air stops coming out. The blower works, and the heat pump is on but no warm air is coming out. I have to set the thermostat to off for a few mins and then turn it on again and works again. what could be wrong? the thermostat is a digital one, not programable. i'm thinking is something that has to do with the thermostat but no sure.

Yes, I would start debugging at the tstat to see what signal it is sending to the HP, since, if I understand you correctly, taking the tstat out of heat mode and then back appears to reset something. Does this happen in cool mode as well? Does your EM heat work?

no emergency was not working before the tstat was changed. but i'll play around with the tstat some more and see what i can find. thanks!