My Carrier heat pump seems to be on auxilery heat a lot. I can hear the thermostat click into derost, it runs there for awhile, then it shits off for 20 -30 seconds, then it comes back on in auxilery heat and runs there until it reaches the proper temp. When does the defrost cycle occur? Does it automatically switch over while the heat pump is running or does the heat pump shut down and then switch to the defrost cycle? How long should the defrost cycle last? a couple of minutes or up to half an hour or more?