Troubleshooting Tips for Your RV Air Conditioner/ Heat Pump

by Dometic Corporation

Heat Pumps and Air Conditioners: What’s the Difference?

Simply stated, an air conditioner will cool your vehicle while a heat pump can operate in both a heating and cooling mode. With heat pumps, the flow of the refrigerant is reversed compared to an air conditioner. An air conditioner not only lowers the temperature of the air but also conditions the air by removing moisture and filtering it. Because moisture is involved, humidity is a large factor in how efficient your air conditioner will operate.

Climate-Control Hints

Whether you have an air conditioner or a heat pump in your RV, here’s a list of things you can check before you call for a technician:

1. If the air conditioner/heat pump doesn’t run (the fan and/or the compressor), check the AC voltage. If the thermostat has no lights showing, it means it is not receiving DC power. The 12-volt DC fuse should be checked. You may also want to look at the breaker at the electrical source. To check your AC voltage when you arrive at your destination, plug in your electrical cord. Inside your vehicle place a voltmeter into a receptacle and start your air conditioner or heat pump. When the compressor starts after a two-minute delay, check your voltage. It must be over 103.5 volts for the air conditioner to operate.

2. When the fan runs and the compressor tries to start but won’t run, examine the exterior heavy-duty long extension cord, receptacle and plug. If those are in working order, check the AC voltage.

3. If the fan runs, but the compressor cycles on and off and doesn’t cool correctly, it could be improper or poor air flow, a dirty filter, dirty condenser, short cycling (a duct leak) or the AC voltage may be the problem.

4. If the compressor doesn’t cycle at all, a qualified technician should check the filter (which must be clean) and the condenser. It is important to check the condenser to determine if it is blocked. The condenser is visible with the Brisk Air units, but the Penguin air conditioner shroud will need to be removed for inspection. If the condenser is blocked, the debris will need to be removed by a technician.

5. Poor or improper air flow, short cycling, a dirty filter or placing the thermostat on its minimum temperature setting and the fan on low speed in high humidity situations can cause evaporator freeze-up.

6. It’s leaking! What should you do? First, this is something that should be repaired by a certified techni- cian. The technician will take a good look at the mounting bolts, roof gasket and condensation drain holes. It is also good to be sure the technician checks for roof damage.


The unit when it is switched on to cool/auto fan it will blow cool air and immediately but not always blow warm air and you can hear what seems to be the compressor cycle back and forth between cool air and warm air. Eventually but not always it will blow cool air continuously. When it blows warm air continuosly it gets to warm and i will shut it off and use the rear unit.

Is it the reversing valve, if so is it a bolt on item, or maybe the start or run capacitor. Sometimes it will work for days with no problems


The first thing I would do is a hard re-set on the controller. This is the first thing I always try when a AC unit is having troubles. With the thermostat ON, hold the TOP and BOTTOM button at the same time, turn the thermostat OFF then back ON and let go of the button the letter FF should appear, this will tell you the system is reset.

Just a note on the capacitor's... I have seen allot of these go bad.. The majority of them will melt the wiring on the caps of the capacitor. I wanted to mention this because it is something to look out for. Remember never touch two post of the capacitor at once they do store energy and can give you a serve jolt.

This does sound like a reversing valve issue, one way to check is to feel the refrigerant line at the top of the inside coil. In the cool mode this line should be cool to the touch, in the heat mode the line should be warm or hot. IF you do not feel a cold line in the cooling mode,the direction of flow is not correct. You can check the solenoid coil for ohms/continuity, A open circuit shows the solenoid is defective, you should see around 465 ohms +/- 10%

When you ask for cool air, it then switches over so the coolant will start to circulate. It is most likely due to the outside temperature. These heat pumps will NOT operate correctly or efficiently at outside temperatures of around 40F-45F or below. There just isn't enough heat to extract from those temperatures. That's when you break out the small electric ceramic heaters.

What type of furnace? strip heat....gas... I would check the reversing valve.Run the unit in cooling have someone switch the stat to call for heat....."Whooosh!!!" the reversing valve will switch over.Other methods of switching the valve , remove one wire, remove the nut and slide the solenoid off the valve will reverse. The switching solenoid can be checked magnetically by using a small screwdriver. Switch from cool to heat or heat to cool this way you can check if the valve is getting a signal .

Heat pumps are a fairly complicated simple device..... sometimes just switching the valve back and forth a couple times gets it unstuck. Remember air coming from the duct will feel cooler than air from a gas furnace .

Most customers don't think they are working when they really are. 100 degree heat is not that hot to 98.6 degree person who is used to 120 degree gas heat!

© Barry Brideau 2003-2017