Arrived and found coil temperature sensor unplugged. I plugged in the sensor and tested the defrost cycle. The unit is frozen solid and will take awhile to thaw out. The system is dual fuel and I have the thermostat set in emergency heat to operate the gas furnace until the outdoor unit melts. Customer signed arch form for monthly membership, the service call fee was waived for or customer becoming a member. I was only going to charge the service call fee because the unit is frozen, fee was waived. The office will call to set up the heating maintenance. I did not have time on this weekend to perform the maintenance and the heat pump needs to thaw out first.