RV Rooftop Air Conditioning - Dometic Corp


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Frequently Asked Questions

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. Is that normal?

Answer: The simple answer is yes. For overall best results:

  1. Set the thermostat at the desired temperature level.
  2. Select the fan speed that best satisfies your needs.
    • HIGH COOL: Selected when maximum cooling and dehumidification are required.
    • MED. COOL: Selected when normal or average cooling is required.
    • LOW COOL: Selected when room is at desired comfort level and needs to be maintained. Normally, Low speed used for nighttime operation.

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. What should I do?

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:

  1. Turn the selector switch to "OPT HEAT".
  2. The heat strip will come on and begin heating.
  3. When desired temperature level in RV is reached, move the selector switch to "OFF" position or "FAN" position. Thermostat does NOT control the fan/heater ON/OFF cycle.

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. If this occurs:

  1. Inspect the filter and clean if dirty.
  2. Make sure air vents are open and not obstructed. Units have a greater tendency to frost when the outside temperature is relatively low. This may be prevented by adjusting the thermostat control knob to a warmer setting (counterclockwise). If frosting continues, operate on any FAN ONLY setting until the cooling coil is free of frost; then resume normal operation.
  3. If frost condition persists, contact your local service center for assistance.

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:

  1. Parking the RV in a shaded area.
  2. Using window shades (blinds and/or curtains).
  3. Keeping windows and doors shut or minimizing usage.
  4. Avoiding the use of heat-producing appliances.

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?

Answer: If your unit fails to operate or operates improperly, check the following before calling a service center:

  • If RV is connected to a motor generator, check to be sure the motor generator is running and producing power.
  • If RV is connected to power supply by a land line, check to be sure line is sized properly to run unit load and it is plugged into power supply.
  • Check your fuse or circuit breaker to see if it is open. Insure fuse is not burnt, or circuit breaker is "ON" and not activated.
  • After performing the checks listed above, call your local service center for further help. This unit must be serviced by qualified service personnel only.

When calling for service, always give the following:

  • Unit model and serial number found on the identification label located on base pan of unit bottom. Return air grille must be removed from air distribution box to view.
  • Air distribution box model and serial number found on rating plated located on ceiling template. Observe this rating plate through the filter opening.

For more information about Dometic RV rooftop air conditioners, please visit the Dometic RV climate control systems website location.

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