Arrived at the customer’s home to find the cause of their heat pump being frozen. Tested heating and auxillary heat from the thermostats. Measured the electrical component readings and refrigerant pressures. Found that a wire for the system defrost was disconnected, preventing the defrost cycle from taking place. Reconnected the wire and tested operation. Changed the defrost timer from every 90 minutes to every 60 minutes. Also noticed that the system next the unit was very loud and likely will have a bad fan motor before too long. Reported findings to the customer. Also changed the 16x25x4 media filter during today’s visit.