What maintenance does my RV roof air conditioner require?

Dear Dave, 
What is involved with maintaining my RV’s roof air conditioning unit? Thank you! —Randy

Dear Randy,
You did not provide a make and model of your unit or the air conditioner, so I will assume you have either a Dometic or a Coleman-Mach Airxcel. Both have similar recommended maintenance.

One of the most important maintenance items, in my opinion, is to regularly inspect and clean the return air filter. Whether you have a roof-ducted or direct-flow unit, there is a return air filter that pulls in the warm, moist air from inside the coach and draws it over the evaporator coil. Typically, this is a plastic open-cell material that can be washed with soap and water, dried, and reinstalled.

The direct-flow units will have the filter on the air conditioner, while ducted models may have a separate air intake in the roof.

Check the mounting bolts every year

Your roof air conditioner is sandwiched to the roof material with a metal plate inside and four mounting bolts and a gasket between the outside unit and the top of the roof. This gasket can shrink or become loose and allow moisture to penetrate if the bolts are not tightened periodically. Some roof air manufacturers even have a torque recommendation. However, I just take the inside shroud off each fall before storing my unit and snug them up by hand with a socket.

If these bolts are not inspected and tightened each year, the gasket will get loose and not seal, resulting in moisture penetrating. It could eventually ruin the roof, as in this 1996 Jayco.

Inspect and clean the evaporator coils of roof air conditioner

The fan draws warm, moist air from the inside and pulls it through the evaporator coil that has coolant lines running through it. Even with a filter, dust, dander, and other items can get through and collect on the evaporator fins. That will block airflow and make the unit run at a high amperage and eventually ruin the compressor.

Each year it is important to inspect the coils and clean them off with either a shop vac from the inside or water and cleaner from the outside. Be careful and cover the return air intake to keep water from getting inside the coach.

It is also important to inspect the drip pan and weep holes to make sure they are clear so moisture can flow out.

Here is an example of a blocked evaporator coil that resulted in a new air conditioner. This was caked with body powder!

Check for proper air flow and temperature

I like to check the vents for proper air flow and temperature in the spring and fall just to verify the unit is operating as designed. I use an anemometer at the vents and look for consistent airflow, which is measured in cubic feet per minute (CFM). It should be somewhere between 400-500 CFM. You should be able to get a recommendation from your RV manufacturer. If it is low, you have a blockage somewhere or the fan is not running fast enough due to failure or low voltage. The temperature should be 16-20 degrees cooler than the return air temperature coming into the unit.

Clean and straighten the condenser coils

On the back of the unit there are coils that help bring down the temperature of the coolant that just ran through the evaporator coil. The reverse side of the fan fins draw outside air in from the back or sides and blows out the side. If the coils are damaged or dirty, there will not be sufficient airflow drawn in to cool it down and it will not run as efficiently. If the coils have been flattened by a tree branch or hail, you will need to straighten them out with a small screwdriver or fin comb like this one from Amazon.

Cover the unit when in storage

I like to cover the entire coach when storing and especially the air conditioner, as it keeps moisture away from the fan motor and bearings. Also, a good tight wrap around the entire shroud can help keep “critters” from nesting inside the insulation around the fan. This unit had a squirrel family living inside the shroud and come spring had a snowfall of insulation beads when the air conditioner was fired up!

 You might also enjoy this from Dave 

How can my RV’s roof air conditioner run more efficiently?

Dear Dave,
I’d like to improve the efficiency of our roof air conditioner. The factory shrouds are black. I’d like to paint them white. Second, I’d like to insulate the pipe from the compressor to the evaporator. Thanks. —Joe, 2019 Coachmen Pursuit

Read Dave’s answer.

Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”

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