Thursday, March 15, 2012

RV AC Repair and Troubleshooting and RV Air Conditioner Maintenance Tips

Today's efficient rooftop RV air conditioners are made to provide many years of comfortable cooling as most are used during the hottest part of the year. If maintained properly, an  AC is normally trouble free except for changing or cleaning the filter regularly.

But like all appliances, an AC unit occasionally requires cleaning or even repairs in some cases. The following tips are intended to assist a travel trailer or motorhome owner to clean or troubleshoot any RV AC problems you may encounter, to repair the AC unit, or find parts for repairs needed.

Common RV AC problems will be addressed as will be the solutions. The questions addressed are actual queries to me from RV owners concerning rooftop AC problems as are the solutions the owners reported. I hope you find this article helpful and feel free to pose your own questions.

How An RV Air Conditioner Works

The main parts of a rooftop air conditioner consists of a sealed compressor which pressurizes and circulates freon though two coils to not only remove any heat from the air circulating through the interior, but to exhaust this same heat to the outside of the RV itself.

The AC fan motor operates a squirrel-cage type fan to pull the cool air through one of the coils and, on the same shaft, a regular type propeller fan to blow the hot air through the other coil so it will be exhausted directly outside of the AC unit.

Both compressor and AC fan motor  utilize a capacitor to boost the power of each on start up to prevent the electrical circuit from overloading and tripping a breaker.  Your RV AC unit may have only one capacitor to start and run both fan and compressor, or each may have a separate capacitor.

The remaining items consist of the thermostat-either wall mounted or in the unit itself-a power switch, and various relays and circuit boards.  These will be discussed later in the article.

RV Air Conditioner Maintenance Tips

Cleaning the RV Coils

Perhaps one of the most common AC problems experienced by owners is caused by having dirty coils in the unit.  The coils-similar to an auto radiator- must be clean enough to allow the cool and hot air to pass easily through the small opening in the coils.

After several seasons of use, these coils will begin to gather dust and other debris in the coil openings causing the efficiency and cooling properties of the AC unit to be adversely affected.  Seasonal cleaning with a special coil cleaner will make a great difference in the temperature of the air being circulated throughout the RV.

When using the coil cleaner, be sure to cover any adjacent painted surfaces to protect them from being stained or damaged.  Coil cleaning products often contain very corrosive chemicals, so keep this in mind.  This procedure is easily accomplished by removing the AC shroud to access both of the coils.  Be sure to cover the vent leading down into the interior to prevent any cleaner or grime from dripping down inside the RV.

Lubricating the Fan Motor   

Some RV  rooftop units utilize oil tubes to easily lubricate the fan motor bearings to keep the shaft turning with the least amount of electrical power possible.  These oil tubes are normally located right above the fan motor seals on each end of the motor.  Simply add a few drops of machine oil occasionally to keep the bearings well lubricated.

Even if yourAC fan motor has sealed bearings with no oil tubes, it is still possible to spray a good quality lubricant around them to provide a bit of future lubrication.  As always, try not to get oil on the coils or other nearby electrical connections.  Be sure to clean up any excess oil after the lubrication process.

Troubleshooting RV AC Problems

The following text contains real questions concerning rooftop A/C problems with the solutions for you to compare with your own particular A/C unit malfunctions.  If you don't find your problem here, please ask in the comment section below and I'll try to address your queries.

The above unit shows a very dirty coil  which caused the unit to not cool efficiently.  A good coil cleaning solution got it back to it's intended cooling capacity.

 Question -Why does the fan run on my rooftop A/C but the air isn't cool?

Answer -The problem may be several different things. The compressor may not be running properly, or not at all.  It is still possible for the fan to operate normally if the compressor is bad.  It is also possible the freon is low in your unit.  A bad starting capacitor could be the culprit too.  The capacitor on many AC units may start both the fan and the compressor.  A malfunctioning thermostat might not allow the compressor to start, so keep this in mind. 

Solution - Normally, if a compressor is trying to run you can hear it when you turn the thermostat to a cooler temperature.  Often the lights will dim if the unit is having trouble starting as it draws more power to enable it to begin the cycle.  A good thermostat will normally click when it sends the signal for the compressor to cycle.  If it doesn't, then your thermostat may be at fault.

If the compressor does indeed run, then more than likely your unit is low on freon.  The freon charge is better left to a qualified repairman as certain tools are required.  if the compressor is bad--this nay be checked with an amp meter to see if the run/start amps are higher than listed on the compressor--then you may be better off to get a new unit.  Replacement is normally cost prohibitive.

Question - How do I check the capacitor if I suspect it is bad?

Answer - Using a digital electrical multimeter, set the selector to the OHM setting and place the probes on the two wiring connection points.  A random number should appear and gradually decrease if the capacitor is good.  If this doesn't happen then replacement of the capacitor is required.

For even more questions and comments check out this highly detailed RV AC Repair article.


  1. I have a rooftop AC on my 2002 Rockwood popup camper that is not working correctly. When I switch the AC on it sounds like it's running (compressor?) but no air movement is detected and it doesn't get cool. The AC unit cycles on/off but no cooling results. Even just in the fan setting there is no air movement detected. Any troubleshooting ideas or suggestions?

    1. It may be that the fan is not tightened securely to the fan motor shaft, Chris. You may check this by removing the rooftop A/C shroud. If the motor is bad it should overload and shut the unit down or trip a breaker.


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  16. Pretty good article! Air Conditioner is playing very important role in our life. Thank you for sharing it and I appreciate your efforts.

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  22. Thanks, I have been trying to repair my rv here in Phoenix, the A/C unit went out this last week, and this has helped me understand how they work a little bit better.

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  29. Hi,
    I owne a 2000 Fleetwood Southwind RV with 2 roof AC, when i turn on the fan on the bedroom AC it turns normally but when i switch to LOW COOL or HIGH COOL the AC motor comes on but a strong burning odor enters the bedroom, could this be due to a faulty STARTING CAPACITOR. If so where is it located and what does it look like can we see a picture of it. Thank you for your help. John.

  30. Hi,
    I was running my AC unit this weekend in the AUTO position. When the camper reached temp the fan kicked off but I could still here the condenser unit running. I switched the thermostat to the OFF position and the condenser continued to run. I had to flip breaker to get it to stop running. When I flipped the breaker back on the condenser unit started to run again even with the thermostat in the OFF position.
    Any ideas?

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  32. In my 2006 Day Dreamer 5th wheel, our Dometic A/C (13,500 BTU) in the bedroom works ok, but when we turn it off, or it shuts down after a hot day, it starts to leak into the bedroom. Investigation shows that ice is forming on the intake side and starts to melt, leaking into the bedroom. What might cause this ice, and how can it be fixed? I appreciate your assistance on this.

  33. A good service call will focus on a lot of different things. When your technician arrives, you can expect several steps to take place like coolant level check and refill if needed, full check of temperature levels, cleaning of condensing unit coils and check of amperage draw of the compressor unit. Harrell Home Services technicians have decades of experience working with air conditioning and heating systems of all makes and models.

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  36. I think that ac is vital to any road trip. In my pre-trip check up of my RV, I always check the ac twice. I can't drive or function without it! I like going south a lot because my family lives out there.

  37. Thanks for the great information. I've been trying to fix my air conditioning for a couple of weeks now, and as of yet I really haven't had that much luck. I'll definitely have to try some of the things you mentioned, and if they don't work out I'll probably just hire someone to fix it for me.