RV AC Not Cooling? 6 Tips to Make it Work Better

As RVers, we all love to get out there and enjoy the benefits of this lifestyle when the weather is fine. Summer is a popular time for camping, and in winter the snowbirds hit the road in search of higher temps. Those of us who RV full-time seek the benefit of warmer weather in every season. The ability to chase the sun is one of the benefits that make the RV lifestyle so fantastic. But if your RV AC isn’t cooling well, then fantastic can turn miserable pretty quickly.

That’s why today we’re offering our 6 tips to help make your RV AC work better. Let’s dive in and cool down!

RV AC Not Cooling? It’s Time to Troubleshoot

The first order of business if your RV AC isn’t cooling is to walk through a troubleshooting process in an attempt to find out what the issue is.

If your RV AC is running, but just isn’t cooling well, we’ve got some hot tips — well, actually, we’ve got some cool tips for you!

Let’s walk through them one at a time to help you figure out why your RV AC is not cooling well… and address that issue with a DIY-able remedy.

1. Park Your RV in the Shade if Your RV AC Isn’t Cooling

OK, this tip is simple but effective: park your RV in the shade whenever possible. This takes some of the pressure off of your AC unit so that it doesn’t have as much heat to contend with when cooling your RV. Solar gain (the increase in heat/temperature caused by exposure to the sun’s radiation) is a large contributor to the increase in temperature inside an RV on a hot day.

While the walls of RVs are insulated, they’re just not thick enough to provide an adequate barrier to the heat from the sun. Parking your RV in the sun raises the level of heat inside considerably, causing your AC to work harder… and likely preventing it from being able to keep up.

So, if your RV AC isn’t cooling as well as you’d like, try this simple tip for starters.

2. Insulate Windows and Roof Vents

Another simple, yet very effective, way to lower the temperature in your RV naturally, is to insulate your windows, roof vents, and skylights from the effects of the sun. Windows and skylights let the radiant heat of the sun through, warming up interior parts and then trapping that heat inside. And roof vents are just thin plastic and aren’t designed to block much heat.

Reflectix, a product that combines what is essentially bubble wrap sandwiched between two sides of reflective film, is very easy to use and widely available at hardware and home improvement stores, or via Amazon:

It can be placed in a window as is (it’s flexible and self-fitting so it conforms to the window and stays in place nicely) and provides excellent insulation as it reflects the heat of the sun from your RV windows, thus keeping it from penetrating into your RV.

Insulating roof vents and skylights is important too, as they allow the sun and its heat to enter the RV, raising the interior temperature considerably. You can DIY roof vent and skylight pillows or you can buy a product like this vent and skylight insulator if the measurements work for your RV.

3. Clean or Replace the Inside Air Filter(s)

Some RV AC air filters are disposable and must be replaced with new filters, while others are washable. This project will vary depending on which type you have. Your filter(s) may be located in one of two places: (1) behind the panel in your RV’s ceiling where the air blows out of (and returns to) the air conditioning unit on the roof or (2) if your RV has ducted air conditioning like in our Newmar, the filters are located behind each return air duct along the length of the ceiling.

To clean the filter you’ll need to: 

1. Remove the filter from your AC unit and take it outside for cleaning, (or replace it with a new one if necessary).
2. Vacuum the filter with a brush tip, or use a soft brush (a soft toothbrush can work well) to clean the filter manually.
3. If the filter is very dirty (and washable), you’ll want to wash it with warm water and vinegar. Vinegar is a great way to address air-borne pathogens such as mold, pollen, or bacteria (don’t use bleach – you’ll damage the filter). Let it soak for at least 15 minutes – the dirtier it is, the longer you can soak it. Use your soft-bristled brush to help remove any stubborn dirt, dust, and grime remaining.
4. Rinse the filter thoroughly with a gentle stream of fresh water to rinse out both the dust/dirt and the vinegar.
5. Allow your filter to dry completely prior to returning it to the housing.

4. Clean the Coils or Fins if your RV AC Isn’t Cooling

There are two sets of coils built into your rooftop air conditioner that are crucial to the efficient operation of the unit, and if clogged or dirty will definitely contribute to your RV AC not cooling well. First, there’s the condenser coil on the outside (that’s usually visible at the back of the air conditioner, even with the shroud in place), which is where the heat from the refrigerant is released to the outside air. The second coil is the evaporator coil that’s deeper inside the air conditioner, where the interior air passes by in order to be cooled. Both coils may need to be cleaned, though the condenser coil (outside) is easier to access.

Cleaning the coils and fins is a project that should probably be done every year or two depending on how much you travel in your RV (and how often you run it in dusty environments). This requires getting up close and personal with the AC unit on your rooftop, so we’ll begin with a few words of caution as is always warranted with any type of work on your RV’s roof:

• You most likely can walk around (cautiously!) on your RV’s roof, but depending on the design of your RV, you may need to place some boards on your rooftop to distribute your weight properly for roof work. Do so with appropriate care for the roof itself and, more importantly, for your own safety.
• Also, please bear in mind that this process will get your roof wet, and a wet roof can be a slippery roof.
• Finally, if you’re not comfortable climbing up onto your RV’s roof, there’s no shame in that at all! Knowing when to ask for help from a nimble friend or even a professional is what sorts the wise from the unwise — so, take this project on in whatever way works well for you.

What you’ll need:

• Cordless or manual screwdriver (bring a Phillips and a flat blade just in case)
• Towel
• Small tarp or a couple of garbage bags
• Spray cleaning solution (we recommend either Simple Green Aircraft Cleaner, which is safe for the delicate aluminum fins, or AC coil cleaning spray)
• Soft brush
• Shop-vac (not essential, but helpful)
• Hose with spray nozzle, set to a light spray pressure
• A/C fin comb
• Small lunch baggie or another container such as a small tub with cover

What you’ll do:

1. First, ensure that both 120V AC and 12V DC power for the air conditioner unit are turned off.
2. Next, safely establish your position on the roof, and remove the AC shroud with caution. NOTE: AC shrouds are favorite nesting locations for wasps & hornets, and you don’t want a bunch of mad insects sending you flying off the roof. So proceed with caution!

3. Once you’ve removed the screws/fasteners holding the shroud on, (there will likely be four, possibly more), place them in the sandwich bag or covered tub and set them aside in a safe location so they won’t roll off your roof, never to be found again. Note that the shroud screws MAY OR MAY NOT all be the same size, so be sure to note which screws were removed from which holes.
4. If you’re cleaning just the exterior condenser coil, that’s all you should need to remove for access. If you’re also concerned that the evaporator coil needs cleaning (i.e. it’s been a long time since you last cleaned/replaced the interior air filter(s), so you’re worried it may be caked with dust), you’ll need to further dismantle the interior shroud to access it. The screws to remove that shroud may be located under metallic insulating tape, so it may take a bit to locate them.

5. Cover all electrical connections using plastic.
6. Using your towel and garbage bag(s), cover the air vent leading into the interior of the RV so that dirt, debris, and water don’t enter the cabin (THIS IS VERY IMPORTANT).
7. Note that the fins are somewhat fragile, so take care not to bend or damage them during the following steps.
8. First, do a dry cleaning using your shop vac (if you have one handy) and your soft brush. Brush the coils to loosen dirt and debris and vacuum it up.
9. Next, lay your towel down in the area and carefully spray your cleaning solution onto the coils, and allow it to sit for 15-20 minutes, or as instructed on the cleaner. (You’ll want to protect your roof from the cleaning solution, particularly if you’re using an AC coil cleaner.)
10. Be sure your garden hose sprayer is set to a gentle spray, and carefully spray the coils to flush out dirt, dust, and debris. If your AC coils have not been cleaned in many years, you may have a lot of build-up to loosen and remove, and in this case, you may need to repeat the process a few times until the coils are clean and the area is free of obvious dirt and debris.
11. If you brought up a shop vac, use it to remove excess water from the coils and the entire area of the AC. If you don’t have a shop vac, you can use a fan or some compressed air (from the inside out!) to dry the coils. Just be extremely careful not to damage the delicate fins.
12. You can take this opportunity to straighten bent cooling fins carefully using the A/C fin comb (bent fins restrict airflow).
13. Re-attach the AC shroud.

5. Make Sure You Have Enough Power

Sometimes when we think we have a major issue with our RV AC not cooling, what we really have is a low-power issue. There are actually some good ways to address this, though, so don’t despair. Let’s take a look at a couple of ways to manage an adequate power supply when your RV AC is not working well.

If your RV is lacking sufficient power to the extent that your RV AC is not cooling or is not cooling well, a Hughes Autoformer may be very helpful, as this product increases the voltage to your RV while also eliminating the potential for damage to your RV appliances. Hughes Autoformers also have surge and spike protection, which is something every RV needs.

What the Hughes Autoformer does is use a small amount of extra current (amps) in order to boost the voltage available to your RV. This is important because when the voltage at the pedestal sags (i.e. on very hot days when everyone is running their air conditioning), your air conditioner has to pull more amps in order to properly run. The lower the voltage drops, the more current your air conditioner will pull. And that increased flow of current through the wiring can slowly damage your air conditioner (and other appliances).

And if the drop in voltage is low enough, your RV air conditioner may not be cooling because it can’t get enough power to start up. You may hear the fan kick on and start blowing air, but the compressor may not be able to begin running, preventing it from cooling!

By boosting the voltage, your air conditioner can run using its rated current flow, instead of having to draw higher amperage. This will ensure that your air conditioner runs properly AND isn’t being damaged in the process.

Another way to address a low power issue that could result in your RV AC not cooling is to use a soft-start product like the Micro-Air EasyStart. Essentially what this product does is reduce the power required to get your air conditioner compressor started up. 

Your air conditioner (and likely your refrigerator’s compressor along with other appliances you may use) require significant power to start spinning. If that power is not available and delivered, then the appliance won’t start. A soft-start like the Micro-Air EasyStart effectively reduces the start current by 65-75% so that your AC can operate on limited power.

So, not only can you run your AC, but you can run other appliances at the same time. Or if you have a large motorhome, you can run two AC units as we do at times of extreme heat (note that each AC unit requires its own Micro-Air EasyStart unit installed).

If your RV AC isn’t cooling, make sure you have sufficient power available to run the unit, and if you don’t, consider options that lower the power requirements on start-up.

6. Keep Your Generator Tuned Up for Running Your AC Without Hookups

It’s great to have a generator to fire up whenever we need additional power when we’re off-grid. But if your generator isn’t kept in good running order and tuned up to deliver adequate power to handle your power demands, then you’ll find yourself with some appliances that won’t function optimally, including your RV’s AC.

Be sure to change your generator’s oil and keep it tuned up in accordance with the specifications of the manufacturer of your generator.

We like to take care of our Onan generator maintenance ourselves, and we’ve made several YouTube videos explaining how we do that. For instance, on a regular schedule, we change the oil, replace the fuel filter, and change the coolant.

But if you prefer to leave generator maintenance to the pros, that’s also a fine approach. The key is to keep your generator in top running condition so that it will continue to run appliances like your RV’s AC very well.

No More Trouble With Your RV AC Not Cooling!

As you can see, once you’ve investigated the source of your RV AC not cooling, there are many ways to address the problem. Depending on your particular situation, these suggestions will either lead you to a satisfactory solution, or to a professional if your AC unit requires repair.

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