Although there have been several articles written about RV maintenance, including my own, some of them fail to address the maintenance requirements of the rooftop air conditioner. This is mainly because for the most part this appliance requires very little attention. With the arrival of the hot days of summer (for many of us), spending some time performing simple maintenance on the AC unit will ensure you keep a cool rig.

I’ll start off with a primer outlining how the air-conditioner works. Like the fridge in your home, the AC unit works on the principle of the Refrigeration Cycle. The primary components of the air conditioner are the refrigerant, compressor, condenser, expansion valve, evaporator, and connecting tubing. The entire cooling process follows the laws of thermodynamics, which are outside the scope of this article. It is enough to mention that a liquid changing state to a gas absorbs heat, whereas a gas changing to a liquid sheds heat.

The cycle starts at the compressor, where low-pressure refrigerant gas is compressed to high-pressure. This flows through the condenser, where it sheds heat to the outside of the RV as it changes state into liquid. The liquid is metered through the expansion valve where the pressure is lowered. This liquid then enters the evaporator, which has the warm RV interior air flowing over it. As the liquid refrigerant flows through the evaporator, it absorbs heat from the surrounding air as it is converted back into low-pressure vapor. The cooled air is returned to the interior of the RV.

This refrigeration cycle runs continuously, with the refrigerant constantly changing state from vapor to liquid and back again. The system will continue this process for many years with only minimal maintenance.

There are really only three main things that you need to do in order to keep your air-conditioner running reliably. The first is to keep the intake filter clean, and be sure to keep it in place at all times. If your AC unit is non-ducted, the filter should be installed on the ceiling shroud between the intake grille and the evaporator coils. If you have a ducted system, there may be a filter in each of the ducted air intakes. Simply wash the filter with water, wring it, and allow it to air-dry before re-installing. If a filter becomes damaged, be sure to replace it with a new one. A dirty filter can impede the flow of air over the evaporator coils and reduce the efficiency of the unit. A damaged or missing filter can allow dust and debris to accumulate on the evaporator. This is not good for an air-conditioner, as debris reduces the heat transfer efficiency and can lead to eventual failure of the system.

Ensure that the condensation that drips off the evaporator (resulting from removing moisture from the interior air) is properly draining away from the AC unit. It is common for leaves or debris to block the moisture drain and flood the air conditioner pan.

The last important maintenance step is to ensure the evaporator and condenser fins are not damaged. Regular inspection of the fins is recommended. If you find crushed or damaged fins, use a fin comb (available at larger RV parts retailers), dental pick, or other appropriate tool to straighten them.

About the Author:

Steve Froese, an avid RV owner, traveler, and  Coach-Net member since 2013, is the principal of “A Word to the Wise Technical Communications”, a published RV author, certified RV technician, and licensed Professional Engineer. He frequently collaborates with the “RV Doctor”, Gary Bunzer, and has worked with the RVIA/RVDA as a technical and training writer and consultant. Professionally, he works as a quality engineer and musician. Watch for more of Steve’s work in upcoming Coach-Net publications.