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RV Air Conditioners

Air Conditioner (A/C) questions and problems are very common to most RV’ers. Often, with little maintenance these units provide many years of efficient operation. Most RVers complain that the A/C is not cooling the way that it should and ask for it to be recharged. Most all RV air conditioners are factory-sealed units and these units should never require recharging, unlike your automobile or RV dash air. Most recreational vehicle A/C units are very similar, with only minor differences. The most prevalent problem with recreational vehicle A/C units is a dirty filter which reduces air flow and causes dirty evaporator coils, freezing up and efficiency problems, to name a few. Diminished cooling performance is usually a dirty evaporator coil from lack of filter maintenance or smoking indoors. The evaporator coils can be seen with a light, when the filter is removed. They are vertical coils and fins that look similar to a silver radiator when clean. When dirty, they appear gray, brown or black, and in severe cases, it looks like a cloth blanket covering the coils. Dirty coils greatly reduce the efficiency of the A/C unit and it can also cause the compressor to overheat. The evaporator coil must be clean to properly conduct the heat from the air. A qualified professional technician should clean dirty coils. The process is complicated and requires service from the roof, special caustic cleaners and partial dis assembly of the A/C unit. Recreational vehicle A/C systems are designed from the factory not to be recharged for the life of the unit; therefore the Freon levels cannot be checked easily. There are only two common performance tests using thermometers and an amp meter. The RV’er can perform a temperature performance test with two thermometers. One is
used for ambient room temperature going into the A/C filter and the other thermometer is to measure the cool air exiting the discharge vent closest to the A/C unit. The A/C should be set to maximum cold and should run for at least 30 minutes. The factory specification is approximately 20°F cooler air exiting out the discharge, than the ambient room temperature entering into the filter. Air conditioners only remove the heat from the air, so if your RV temperature inside is 90 degrees the discharge temperature would only be approximately 70 degrees.
Most RVers, coming from a cooler and drier climate, complain about poor A/C performance in a hot and humid climate. The RV itself can be the problem. Lots of windows, vents and poor insulation will result in uncomfortable conditions. Remember the A/C discharge temperature is only 20 degrees cooler than the inside temperature. Parking in a shaded area and closing window shades will help overcome this problem. The RV may require a larger or an additional A/C unit. Operating the A/C in extremely humid conditions will also reduce efficiency due to water droplets on the evaporator coil acting like an insulator, reducing air to coil contact. Closing off vents and restricting the
airflow will also reduce efficiency. A/C units sometimes freeze up at night in high humidity conditions when fan speed is set to low. Operate the fan speed on high when operating in these conditions.
If the A/C condenser coils, which are located on the roof at the outside rear of the A/C, are clogged, damaged or bent, it will greatly reduce efficiency.
Another common problem is the 30 or 50 amp voltage supply being too low. Operating voltage should be at least 105 volts AC. A dirty plug connection, using a long or small extension cord, electrical adapters or a burnt shore power receptacle outlet are the most common causes of compressor overheating and failure. Never use a 15/20 amp electrical adapter when operating an A/C unit. A 30-amp service is only capable of
running one A/C unit. A 50-amp service is required to run two or more A/C units.
Basement central air units have two compressors and should always use a 50-amp service or have a power management-shedding device to disable one compressor when operating on a 30-amp service.
It is recommended to have a receptacle mounted volt meter for 30 amp service or two receptacle mounted volt meters on different circuits to monitor the line voltage for 50 amp service at all times. You can easily see low or high operating voltages to your RV. Many campgrounds have inferior wiring and worn out receptacle outlets. Another great alternative is to have a line conditioner surge protector installed in your RV or an external surge protector that your RV outlet can plug into. A 50 amp unit is especially susceptible to major damage to all the electrical appliances and accessories from an over voltage condition caused by a bad common outlet terminal. A line conditioner and surge protector can save you lots of money and headaches.
Most A/C units have a thermostat and a control board that require a good 12-volt DC supply and 120 volts AC to operate. If the unit does not turn on, check the AC circuit breaker that supplies the A/C unit. Reset it, if necessary, by firmly pressing it completely off, then press back to the on position. A good indicator of a good 12-volt DC supply is to listen for a clicking sound from the control board when the A/C thermostat is turned on. The board is usually located above the A/C filter. If a click is not heard, check the 12 volt DC fuse in the fuse panel or verify that you have a good 12
volt DC supply as described in the article BATTERY MAINTENANCE.
Some RV’ers complain of water intrusion around the A/C unit from rainy weather. A poor seal between the A/C unit and the roof can cause this. This gasket will compress over time and require an occasional tightening. It can be tightened by accessing the 4 bolts facing down located in the four corners when the filter cover and housing are removed. The gasket can be inspected at this time. If it is less than ½ inch thick, it should be replaced. Do not use excessive force or distortion of the A/C sheet metal can result in fan motor binding or produce noises. While the cover is off it is recommended to flood the roof with water to inspect for leaks. If it continues to leak the gasket must be replaced, because it has compressed too much. Never attempt to use a sealant to glue down or glob around an A/C unit. This can ruin a roof as well as making removalof the A/C unit almost impossible.

Remember that no person should ever attempt repairs on a RV air conditioner without proper training, licensing, tools and access to the correct technical information. Hopefully, this information has been of great value to you. If you have performed these tests or do not understand how to perform these tests, and your A/C unit is not performing properly, it is time to call a qualified professional at (850) 866-6999 or visit https://www.rvtrax.com to correct the problem.