Monday, April 4, 2011

Heat Pump

Newer LD's come equipped with an air-conditioning unit that also includes a heat pump. Several owners have reported problems:

Question: The heat pump compressor cycle would not shut off no matter how low I set the thermostat - it just kept pushing out hot air. Conversely, I couldn't get the A/C compressor cycle to run no matter how high I set the thermostat. I have a Progressive surge/voltage protector that cuts power off at 132V. This happened prior to my problem and I noticed that the voltage was at 153V after the cut-off. When I got home, I took the LD to a service center and, guess what, the dang thing worked perfectly during the following two days of testing.

Response 1: When you experienced the problem, did you by chance switch the thermostat to the OFF position. If you did and the unit continued to run, it is probably fair to assume the thermostat is not the source of the problem. It is possible that the control wire that issues a call for heat was somehow shorting to a "hot wire" causing the problem, though this too seems unlikely. The controls appear (to an unfamiliar eye) to be mostly electronic on the control board, including the relays that start/stop the compressor/fan motor, reversing valve, etc. I would be suspicious of something "sticking" on the control board causing the problem you experienced. This could be a leakage through a solid state device holding a circuit in when it shouldn't be for example. Did you stop the unit finally by turning off the breaker? If so, when the power was turned on again, the problem was gone because the board was "reset", clearing the problem. I suspect that the high voltage was too much for some of the SS circuits on the control board rather than the t-stat. It may be worthwhile to do a little more research with the repair center or on line to see if there is a service bulletin on this problem.

Response 2: Our 2010 heat pump lost it's freon via a leak in the small tubing by the compressor (it kept working but no heat or cool). There was oil around the area where the freon leak was located. You might check the inside of the cover for traces of oil. It could not be repaired and Dometic replaced the entire unit under warranty.

Editor: Loss of freon is not likely to be the cause of the OP's problem. With no freon, there would be no heat output.

Contributors: dandfridley, Mike Coachma, roadienh3