Bruce Bernhart RV FAQ's


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Original articles plus the "best of the web" on beginning and advanced RV care and maintenance by RV writer and enthusiast Bruce Bernhart

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Kansas City  •  Chicago  •  North Carolina

Updated June 30, 2013

RV Care and Maintenance Topics: Air Conditioners

In Minnesota, Bruce Bernhart has been an RV and camping  enthusiast since the mid-1980's

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Tips on Care and Maintenance of the RV Air Conditioner

  • Clean the filters at least every two weeks when the air conditioner is in operation. Running the unit with dirty or clogged filters will decrease the flow of air across the cooling (evaporator) coil, potentially causing the coil to freeze up. If the air conditioner is running for long periods of time with dirty/clogged filters, a potentially expensive cleaning of the evaporator coil by qualified service personnel may be necessary.
  • If your motor has oil ports, we recommend using SAE 30 weight non-detergent oil. The motor requires only 1-2 drops of oil per year. DO NOT OVER OIL. The oil ports will be visible on the fan motor with the unit's plastic cover (shroud) removed.
  • Clean the outside (condenser) coil at least once a year. Blow out any debris which may have collected on the coil. Since the A/C fan pulls air in through the back of the coil and exhausts it from the sides of the shroud, it is best to blow compressed air through the coil from the inside out. You may also wash this coil with water if you choose to do so. Please remember to disconnect all power to the vehicle/air conditioner first.
  • Finally, you should inspect the air conditioner and its housing. If the housing is loose or cracked, the seal that prevents water and moisture to enter the RV could be damaged. You should also look at the condenser fins and make sure none of them are bent or damaged. Air conditioner fins aren't typically replaceable, and many times they cost as much as a new air conditioner. You should also wash the exterior of the air conditioner and remove any bugs, road tar, or other debris on the exterior of the unit.
The coils, the compressor, and the motor of a room air conditioner are sealed components, so any repairs to them should be left to a professional service person. However, you can make minor repairs, and regular maintenance will keep your unit running well. When extensive repairs are needed, you can also save the cost of a service call by removing the air conditioner from its mounting and taking it to the repair shop.

During the winter, room air conditioners should be protected from the elements. Either remove the unit from its mounting and store it or cover the outside portion of the unit with a commercial room air conditioner cover or with heavy plastic sheeting, held in place with duct tape.

Caution: Before doing any work on a room air conditioner, make sure it's unplugged. Room air conditioners have either one or two capacitors, located behind the control panel and near the fan. Capacitors store electricity, even when the power to the unit is turned off. Before you do any work on an air conditioner, unplug it and discharge the capacitor or you could receive a severe shock. The unit's owner's manual will show the location of capacitors and tell how to discharge them. Otherwise, let an air conditioning technician do it.

More Advanced Topics:  Understanding How the Relay Works:

So what is a relay? A relay is defined as an electromagnetic mechanism moved by a small electrical
current  in a control circuit (12VDC in this case). How does this relay work? As this mechanism
moves back and forth in the relay it will open or close a set of contacts capable of carrying high
voltage and (115VAC in this case). All of our control circuit relays are normally open and the
contacts close as power from the thermostat is applied.  The 115VAC power to the compressor is interrupted
by a set of normally open contacts on the relay. In order for these contacts to close 12VDC must be applied by the
wall thermostat to the relay coil. When the thermostat switch is placed in the cool position 12VDC(+) travels from
the thermostat red wire to the thermostat yellow (Y) wire and then to the relay coil. When the coil is activated an
electromagnet inside the relay will pull the contacts closed.  The 115VAC will now operate the compressor until the
thermostat opens or the system switch is turned to the off position. The entire control circuit for the A/C  Heating
system would include the rest of the thermostat functions and possibly 2  or 3 more relays. In addition to the compressor relay you would need a separate relay for Low Fan, one for High  Fan, and possibly one for Heat, if a heat pump or electric heating element is used.

Thermostat Location:

All of the air conditioning functions are controlled by the wall mounted thermostat.  These
thermostats utilize a 12 VDC electrical circuit which is supplied by the vehicle manufacture or the
installer of the A/C unit. Most of the thermostats provided by Recreation Vehicle Products 
are combination (Heat / Cool) thermostats. These thermostats are capable of operating both the
roof top air conditioner and any furnace with a 12 VDC control circuit. Thermostats are really nothing more than
temperature controlled switches. When the need for Cooling or Heating exists the thermostat sends a 12VDC(+)
signal to the control relays or a P.C. board which in turn energizes the air conditioner components or the furnace.
Thermostats are very sensitive instruments. For accurate temperature control and comfort the following
considerations for thermostat locations should be taken into account:
1. Locate the thermostat on an inside wall about five foot above the floor. Pick a dry area where
air circulation is good. The thermostat should be mounted within a reasonable distance from
the appliance the thermostat will control. This will assure a more accurate temperature
relationship between the thermostat and the appliance the thermostat will control.
2. Do not install the thermostat where there are unusual heating conditions; such as direct
sunlight, heat producing appliances (television, radio, wall lamp, etc.); or a furnace or air
conditioner supply register.
3. When installing or servicing these thermostats the technician should take all necessary
precautions not to short any positive wire to ground. Permanent damage to the thermostat
may occur. Make sure all connections are good and tight. Loose connections may cause
relay chattering which leads to welded relay contacts on air conditioner printed circuit

Remember, you must first verify the 115VAC power source to the Air Conditioner Control
Box Assembly. If the 115VAC power source is NOT present, all of the Air Conditioner functions will
be dead and power must be restored to continue. 115VAC power must be present to the Circuit
Board if any one of the Air Conditioner functions are working.

Russ and Tiña DeMaris on offer these other important tips:

AT ANY TIME that you use a generator to run any load, be sure to have all loads turned off when you start the generator. And when you're ready to shut the generator down, FIRST turn off all loads.

Two air conditioners?  Some big RVs have two air conditioners--and your rig will wired for 50 amp service. If you stay at an RV Park where you can't get a 50 amp hookup, you'll be using an adapter to plug in your rig. Don't try to run both your air condioners at once on this lashup--you'll only blow breakers and cause problems all around. An optional switching system you can have installed can overcome this problem--but it only serves to automatically swap between air conditioner units.

Can you check Freon levels in an RV air conditioner?

No, unlike air conditioners used to cool a house, an RV air conditioner is very different in the way it cools. Nearly all RV air conditioners out there work on the same basic principle as a refrigerator. RV air conditioners also differ from ones found to cool a house in the fact that it is hermetically sealed (Closed System). Because the AC is hermetically sealed you can see why you cannot get your Freon checked or replaced.

Condenser Fins

Condenser fins are really something you should avoid messing with (call an RV Tech), but it is good to know a little about them so you can know what to look for when maintenancing your air conditioner. If the condenser fins are very dirty, remove the filter on the inside on the ceiling. Get a flash light and look up at the condenser fins, they should be clean and clear. It would be a good idea to call an RV repairman if they are dirty. You really have to be careful not to damage these fins when they are being cleaned.

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Bruce Bernhart RV Topics

Be sure to visit the other Bruce Bernhart RV Websites and Blogs:

Solar power for your RV

The care and feeding of your RV battery

The sport of "geocaching" and RV refrigeration basics

The basics of RV power inversion

RV travel tips and tire care

Advanced discussion on power inversion

Tips on buying a house battery and cold weather maintenance

RV insurance basics

Buying the right generator for your RV and portable power

RV television reception options

Care and maintenance of the RV air conditioner

Top RV destinations

RV long-term supplies and weight considerations

RV insurance- Road protection and bodily injury coverage

RV battery types and winter charging considerations

Deep cycle battery basics

Bruce Bernhart RV Websites

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