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How Do RV Air Conditioners Work? RV AC Repair, Maintenance & Troubleshooting


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Air Conditioning System 101

Air conditioners work through something called the refrigeration process. If you’ve ever thought about how RV AC units operate, this cycle can be explained in easy-to-understand terms.

So, How Do Air Conditioners Work?

The refrigeration cycle is a process by which heat is drawn from the hot air inside a room or vehicle and deposited outside the conditioned chamber.

Because the air outside is usually hotter than the air inside, you might think this is impossible. If you can’t take heat from a colder space and dump it in a warmer space, then how does an RV air conditioning unit work precisely?

The secret is something called evaporative cooling. You may have noticed that wet materials feel cold as they are drying out. This is because evaporation requires heat, and evaporating water draws the heat out of wet materials.

Water isn’t the most efficient fluid for evaporative cooling, though. Other more volatile fluids, such as alcohol and ether, are much more practical. These fluids are called coolants or refrigerants.

The refrigeration cycle requires both evaporation and condensation. Usually, we think of evaporation when we boil water, but boiling our coolant would only add heat to our system, and we don’t want that!

Instead of causing evaporation and condensation by adjusting the temperature, we change the pressure. If we remove pressure from a liquid coolant, it evaporates and absorbs heat. Then, if we add pressure to that evaporated vapor, it condenses and releases heat. 

This is the secret to how an air conditioning unit works. Outside, a compressor pressurizes the refrigerant vapors into a hot liquid. This liquid flows through the condenser, and fans blow air over the condenser to release heat into the atmosphere. 

Once the liquid is cooled down, it flows through an expansion valve into the evaporator. In this step, the coolant liquid evaporates into a gas and expands. This cold gas flows through coils, and fans blow hot air across those coils. This air becomes very cold, and this is what you feel inside your RV.

Explanation of the Parts

There are four main components to RV air conditioner units:

  • Compressor.
  • Condenser coils.
  • Expansion valve.
  • Evaporator coils.


The compressor is the workhorse of the entire system, pressurizing the coolant from around 30 psi to as high as 240 psi! This forces the coolant into a hot liquid state that flows through the condensing coils.

The condenser coils will be located outside your room or vehicle because they can become pretty warm (usually around 125 degrees Fahrenheit). These coils must be hotter than the outside air so that they can cool down slightly and give away their excess heat.

Once the liquid-state fluid is cooled down to ambient temperature, it is regulated through the expansion valve. This valve controls how much coolant flows through the evaporator coils inside the vehicle or room, and this controls how RV air conditioners work.

The liquid coolant flows through the evaporator coils and expands into a gas state, absorbing heat from your room or vehicle, and lowering the temperature to a more comfortable state.

A fifth component, which is often overlooked but necessary regardless, is the fan system. Both the condensing coils and the evaporator coils need to have air blown across them to facilitate the cooling power, and usually, this is accomplished by fans on both sides.

Air Conditioners Demand Lots of Energy

RV air conditioning units work by consuming a lot of energy! It’s not uncommon for your RV AC to use more electrical current than any of your other appliances. Fortunately, there are ways that you can try to conserve energy when using your RV air conditioner.

RV Air Conditioner Efficiency Tips

Running your RV air conditioner efficiently will not only save energy but will also help your AC do its job right and lower the cabin temperature to a comfortable level. Follow these tips to find out to keep your AC system running efficiently.

Routinely Check and Clean Your AC Filters

Just like the AC units in your home, you need to clean or replace your RV’s AC filters regularly. When the filters become dirty, the rooftop air conditioner needs to work harder to force air past the coils. This is work that could better be used for the refrigeration cycle.

The dirty air filters will also slow down the air flow into the cabin, so eventually, you might not feel the airflow at all. 


The worst thing that can happen with dirty air conditioner filters is that they can become contaminated with mold or bacteria. When the cabin air flows through these filters, sometimes the toxins can break free, and you might risk getting yourself or your family members sick.

So, for health reasons, and also to ensure your RV air conditioner runs efficiently, keep your air filters clean. Your RV air conditioning filters can usually be sprayed with a hose and then air-dried, or blown out with an air compressor.

Use Fans, With or Without Your AC

Sometimes, your RV air conditioner might be working fine, but you aren’t feeling the cooling effect because of insufficient cool air circulation. Appliances and furniture inside your RV can obstruct the airflow so that cool air never reaches your seat or your bed.

If a thermostat controls your AC, this control might be malfunctioning due to pockets of colder air near the thermometer. The thermostat works best when the cabin air is at a consistent temperature at every point, and the best way to achieve this is with interior ceiling fans.

Furthermore, fans (and proper cool air circulation) can make a person feel up to 10 degrees Fahrenheit cooler by removing layers of stagnant air that settles around a human body and prevents convection. 

A fan uses much less current than your camper air conditioner, so for all of these reasons, it is much more efficient and practical always to use fans in cooperation with your AC.

Always Park in the Shade If Possible

This should go without saying, but of course, your motorhome camping experience will be much cooler and more comfortable if you can park in the shade during the hot summer seasons.


Obviously, your trailer will be cooler in the shade. The AC coils need to purge heat from the coolant outside the vehicle. It is much easier for the RVs air conditioners to purge that heat in the shade than it would be in direct sunlight. If the outside coils get too hot, the AC unit might not work at all.

Close off Parts of the RV That You’re Not Occupying

You might be lucky enough to have a large, spacious rig. However, this spaciousness can work against you.

Air conditioners are rated by how many tons of cool air they can generate, so an RV with more air inside will be harder to cool than an RV with limited space.

You can help keep fresh inside your RV by limiting the space that your AC is cooling. Do this by closing the doors to bedrooms and bathrooms while they’re not being used. Those spaces might get warm, but the room in which you’re sitting will enjoy the full power of your RV air conditioner.

Avoid Using Appliances That Add Extra Heat Into the Air

You will feel much more comfortable and cool inside your RV if you make sure not to run other heat-generating appliances when you’re using your AC.

Cooking, showering, and running laundry can all contribute extra heat into your RV cabin. When this happens, the AC must work harder to remove this excess heat.


Not only do these appliances contribute heat, but they also draw additional electric current that the AC unit might need to work correctly. After all, how do RV air conditioners work properly without adequate electrical current?

Thoroughly Insulate Your RV

Maybe your AC is working fine, but you’re asking, “How do RV air conditioners work better?” A well-insulated RV will keep you more comfortable not only when using your AC in the summer, but also when camping during the cold winter months.

Lining the walls with fiberglass or rigid foam insulation will prevent the summer sun from turning your RV into a portable oven. It will also prevent heat from escaping your RV during the chilly winter nights.

Fiberglass and rigid foam are trying for a novice RV owner to install, but spray-foam insulation can be a cheap and easy-to-apply solution.


When insulating your RV, don’t forget your windows. RV windows can be a significant source of heat loss or heat intrusion, so it might be worth the cost to upgrade to multiple-pane insulating windows.

Maintaining Your RV Air Conditioner

Performing regular suggested maintenance on your AC unit will ensure that you never have to get a mechanic involved. The following steps are simple measures that you can take to keep your AC running efficiently.

How to Clean the Filter

The AC air filter is usually just behind the interior air vents. Open up the air vent and carefully remove the air filter so that you don’t shake dust and contaminants into the cooling coils.

If the filter is made of woven plastic mats, it can be cleaned easily with a hose or air blower. Take the filter outside and spray or blow the dirt free. Ensure that you thoroughly dry the filter before replacing it in the air conditioner.

If the filter is made from fiberglass with a cardboard frame, this is meant to be disposable. Check your auto parts store or hardware store for replacement filters.

Video: https://www.youtube.com/watch?v=on67V50lHOE

Locating and Accessing the Condenser and Evaporator Coils

Even with regular maintenance of your AC air filter, your coils may occasionally become dirty.

You can access your evaporator coils by removing the air filter on your interior AC unit. You will find the evaporator coils right behind that filter.


The condensing coils are usually located under a casing on your RV’s exterior AC unit. If you remove that protective cover, you’ll find the condensing coils underneath.

Cleaning the RV Air Conditioner Coils

  1. Turn off the A.C. system and disconnect the current at the breaker box.
  2. Remove the casing (from the exterior unit) or the filters (from the interior unit) to expose the coils.
  3. Inspect the coils for any visible damage or large debris. Interior coils, if they have been substantially clogged, can form ice build-up. If this happens, place a pan or a bucket underneath the coils and wait for the ice to thaw.
  4. Brush the coils with a soft-bristled brush to remove dirt and small debris. Frequently wash the brush in warm water to rinse off dust and oils.
  5. Straighten the coils with a fin comb. This is a special fine-toothed comb that will straighten and restore the coils to their original shape and function. Brush the coils in one constant motion from top to bottom.
  6. Rinse the coils with a mild soap solution. You can use a spray bottle and a mixture of dish detergent and warm water.
  7. Allow the soap solution to soak into the coils for 5–10 minutes to dislodge stubborn grease or oils.
  8. Rinse the soap solution off with clean water. Keep the pan or bucket underneath the coils to collect the runoff.
  9. Allow the coils to dry before replacing the filters or casing.

Maintaining the Fan Motor

The A.C. fan motor is a vital component to keep the system running smoothly. Cleaning and maintaining this motor is a similar task to cleaning and maintaining the coils.

  1. Make sure the A.C. system is shut down and disconnected from the current at the breaker box.
  2. Locate the A.C. fan and remove the outer casing to expose the blades and motor.
  3. Clean the fan blades with a wet rag.
  4. Clean the motor shaft and remove any debris that might be entangling it.
  5. Tighten any screws that house the blade set to the motor shaft with a long-tipped screwdriver.
  6. Using a non-detergent motor oil, apply a few drops in any oil ports or motor shaft housings.
  7. If the fan has been malfunctioning, check the motor with a multimeter to ensure that the electrical resistance is between 3 and 30 ohms. Connect the leads on the VOM multimeter to the terminal wires on the fan motor. Low or high resistance means the motor should be replaced or repaired.

Covering Your RV AC Unit When Not in Use

When your RV is not in use, you should cover the external A.C. unit with a plastic tarp to prevent dirt, debris, and precipitation from clogging or damaging the unit. Rainwater or snow can slowly cause rust in the coils that’s difficult to remove.


Cover the unit with a tarp and then use bungee cords to hold it tightly in place. Make sure the tarp is secured against high winds and stormy weather conditions.

Always remove the tarp before traveling, because operating the A.C. unit while covered can overburden the motor or even cause the tarp to catch fire.

RV Air Conditioner Repair & Troubleshooting Steps

If you’re still having trouble investigating how your RV AC system works, try the steps in this troubleshooting checklist.

Step 1: Check the Power Source

Your RV air conditioner might draw as much as 16–20 amps of electric current. If you want to use your A.C., you need to be plugged into shore power at a campground pedestal.


Even the power source connection might only be providing 30 amps of current. If you’re using any other appliances simultaneously while running the air conditioner, this might be causing problems.

Some of the indications that you are having power deficiency issues are:

  • The RV air conditioner won’t turn on.
  • The RV air conditioner compressor not coming on.
  • The RV air conditioner not blowing cold.

You can check the power with an electric multimeter, or by asking the campground manager to check the power station.

Step 2: Find and Test the Capacitors

There are two capacitors in most RV air conditioners. These capacitors store energy to start the motor and run the motor and are essential for AC units to run efficiently. The indications that one of these capacitors is malfunctioning are:


  • The AC fan is not working.
  • The RV air conditioner compressor not coming on.

To troubleshoot the capacitors, you can follow these steps:

  1. Shut off the AC power at the circuit breaker.
  2. Locate the capacitors. They are usually in a compartment on the exterior AC unit.
  3. Discharge the capacitors by shorting the terminals with a flat blade screwdriver.
  4. Remove the electrical leads from the capacitor and then remove the capacitor.
  5. Test the capacitor with a multimeter set to “capacitance mode.”
  6. Compare the multimeter reading with the value printed on the side of the capacitor. 

If the capacitor is bulging in any place, that means that it has overheated and should be replaced, regardless of any measured readings. 

Step 3: Test the Switches and Thermostat With a Multimeter

Your thermostat might be broken, and this can also easily be checked with your multimeter on the “voltage” setting. 

If the thermostat or AC switches are not working, this is the reason stopping the air conditioner from working efficiently. You can order replacement parts from your auto parts store. Note the serial number on the side of the thermostat before ordering.

Step 4: Check If the Fans Are Working

If you can hear the compressor working but can’t feel any cold air coming from your AC, this means the fan is malfunctioning. Remove the vent cover and filters to check the fan behind the coils.

This problem may be solved by cleaning and lubricating the fan motor, or it might require replacing the capacitor (as mentioned above).

If these solutions do not work, you may have to replace the fan motor. This is a task best suited to a professional mechanic.

Step 5: Listen for the Compressor Functionality

You can usually hear when the compressor kicks in. It has a deeper, rumbling sound that’s unmistakable. 

If the compressor is not working, it’s probably not efficient or cost-effective to repair it. The compressor is the hardest-working part of the AC system, and when it breaks, you might need to replace the compressor or even your entire AC. The compressor is the critical component in how RV air conditioners work.


Now that you have a better understanding of how RV air conditioners work, you can travel in cool comfort with confidence. Make sure to follow all of those tips for keeping your RV cold and maintaining your air conditioner.

If you found this article informative and helpful, please share it with other RV owners, especially friends and family members, who might need to know how RV AC systems work. Let’s all make sure everyone keeps cool in the hot summer vacation days!

If you have any more questions, please ask them in the comment section!

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