I have a Bryant 607ENXA42000-TP heat pump, installed in 2015, that has recently developed an odd problem. Five service calls by the dealer/installer and multiple parts replaced have not solved. It's been maintained quarterly, and cools well. What happens is that mostly during the night, the air handler comes on (It's inside the unit, not separate), runs for about 20 seconds, then stops. Then runs, then stops. This happens randomly when the thermostat is not calling for cooling, and while the condenser/compressor are NOT running. Just the air handler cycling on and off for about 15 minutes. Thermostat is a Honeywell digital, and the fan setting is "AUTO", not "CIRCULATE". The oddest part is that I can turn the system OFF at the thermostat and the fan continues running and cycling. So far the technicians have replaced the "control board" and the fan motor itself. But they seem stumped and unable to diagnose. If anyone has seen something similar, I'd appreciate the feedback. Thanks for reading!