Dometic RV Rooftop Air Conditioning Models: 457915.70X, 640312.80X, 457915.71X, 640312.83X, B57915.71X, 640312C35X, 459516.70X, 640312C85X, 459516.71X, 640315.80X, B59516.71X, 640315.83X, 540315.70X, 640315.84X, 540315.71X, 640315C35X, 540316.70X, 640315C85X, 540316.71X Question: The fan in my unit seems to always be on. Answer: The simple answer is yes. For overall best results: The blower runs continuously to circulate air and maintain an even temperature. The compressor will come on as cooling is required to maintain the selected temperature level. Wait at least 2 minutes before restarting the compressor when it has been manually cycled off with either the selector switch or the temperature set lever. Otherwise, compressor will quick-cycle and could result in compressor or supply circuit overload. Question: My unit has the Electric Heater Option, but when it gets colder outside it doesn’t seem to maintain the temperature. Answer: The heat mode of operation will NOT replace a furnace for heating the RV in cold weather.

The intent is to remove the chill on cool days or mornings. For best results when using your Electric Heater Option: Question: What should I do to make sure my filter is clean for maximum efficiency? Answer: Periodically (a minimum of every 2 weeks of operation), remove the return air filter located behind the return air grille and wash it with soap and warm water, let dry and then reinstall. NEVER run unit without return air filter in place. This will plug the unit evaporator coil with dirt and may substantially degrade the performance of the unit over time. Question: What should I do when I notice frost forming on the cooling coil? Answer: Frost on a small portion of the coil is not unusual. Under certain conditions, ice may form on the evaporator coil. This is indicated by very cold output at very low air speed and the icing can be seen through the air inlet hole with the filter removed. Question: What steps can I take when it’s really hot outside and the A/C just can’t keep up?

Answer: The ability of this air conditioner to maintain the desired inside temperature depends on the heat gain of the RV. Some preventive measures taken by the occupants of the RV can reduce the heat gain and improve the performance of the air conditioner. During extremely high outdoor temperatures, the heat gain of the vehicle may be reduced by: Operation on High Fan/Cooling mode will give optimum or maximum efficiency in high humidity or high outside temperatures. Starting the air conditioner early in the morning and giving it a “head start” on the expected high outdoor ambient will greatly improve its ability to maintain the desired indoor temperature. For a more permanent solution to high heat gain, accessories like Dometic outdoor patio and window awnings will reduce heat gain by removing the direct sun. They also add a nice area to enjoy company during the cool of the evening. Question: If my unit seems to be malfunctioning or stops working, are there things I can check before calling a service center?