My RV Air Conditioner Just Hums – Here’s What to Do.


As RV owners, we are typically aware of the noises our rigs make. So much so that we can detect mystery sounds from the “normal” ones right away. When you notice something humming, your investigator instinct immediately kicks in tracing that incessant sound back to wherever it came from. Oh no! Not the air conditioner!

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So, why is my RV air conditioner just humming? An RV air conditioner that only hums can be a sign of many issues, including an easy to fix thermostat problem, oils freezing over, low coolant or a problem with your compressor. This sound may also indicate loose wiring, faulty electrical issues, or very simply telling you that you have dirty coils or a clogged drain.

Keep in mind that humming isn’t the worst sound it could be making. But, ignoring that little hum can result in much bigger problems, if you do not fix it. You probably won’t ignore it for long, especially if it’s not blowing any cool air! Don’t sweat it! With this guide, you will soon be able to chill out in front of an icy cold AC!

Basic RV A/C Troubleshooting

Seeing as there is no one definite answer as to what could be causing a humming noise in your AC unit, we’ll go through a simple step-by-step checklist so that we can eliminate them one by one. Starting from the easiest step to the most technically involved step of this process.

If possible, refer to your air conditioner’s manual for identifying and locating all of these elements.

Circuit breaker. Pop open your breaker box and make sure everything is as it should be. Most RV air conditioning units will also have a reset button, which could give you fan power.

Thermostat. Check your thermostat. What could potentially be the easiest fix ever is a common cause that starts with your thermostat. Does it require batteries? Is the wiring in good condition? Are there any flashing messages on the display screen? Refer to your thermostat manual for troubleshooting these problems.

Loose parts. While you are going over your unit piece by piece, take a closer look at the hardware, and wires to make sure everything is properly tightened and in good condition.

Clogged drain. The safety feature on AC drains prevents overflow into your RV, but can also cause the unit to shut off, or not perform properly. Cleaning the drain tube with a long bristle brush and plastic safe cleaner, then rinse and replace. If your RV has an airflow switch, reset it after you clean the drain.

Frozen coils. Removing your AC vent should expose the coils. If they have ice on them, it means that your AC would not be working as it should and giving off a humming sound. Turn off your unit and allow the ice to melt. Frozen air conditioner coils may also indicate low freon or a faulty thermostat.

Dirty coils. These evaporator coils can often get dusty or dirty and should be cleaned regularly. Allowing dirt to build up can actually cause coils to overwork and freeze, over time.

Coolant. An RV AC unit uses a refrigerant that can be filled if it gets low. But if the refrigerant level isn’t checked periodically, and is run until it’s completely depleted, you will have to get your system recharged.

Intermediate RV A/C Troubleshooting

This section covers the more technically involved steps. A lot of this process can be done by the average RV owner, though you may feel more comfortable leaving these steps to the professionals.

Loose or faulty wiring. Wiring can become loose, or start to fray and malfunction, causing your air conditioner to act up. Before starting any work on electrical wires, turn off the power to the AC for safety. Check the connections, and overall appearance of your wires looking for anything out of the ordinary.

Capacitors. Should your capacitors go bad, your fan motor will not start, resulting in a humming noise. They are typically easy to replace, though general knowledge of electricity is suggested.

Compressor. If you’ve replaced your capacitor, and compressor still won’t kick on, then it, unfortunately, may time to replace it. And by “it” I mean the whole air conditioner.

Fan motor. If the unit will not turn on but will give off a humming sound then there is an issue with the fan motor. Double-check to be sure the power to the AC is off when doing this. You can test if you have a bad fan motor by manually turning the rod. You may be able to feel if it needs to be lubed or breaks free of whatever was preventing it from spinning, which can often be debris that floats in from the air.

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Proper A/C Maintenance for Your RV

We know that getting ahead of problems is ten times better than getting stuck behind them. Which is why routine maintenance on our RV AC units should always be on to-do our checklist

As with most air conditioning systems, an air filter that is placed over the duct should be changed or cleaned periodically. This will keep the air quality high and allergens low. It is typically suggested to change more frequently if you are in a particularly dusty/dirty area. Under normal circumstances once a month is fine.

Cleaning coils regularly will prevent dust & other particles from building up and causing frustrating breakdowns and expensive repairs. Cleaning all around the air conditioner vents and unit keeping it free of sticks, leaves and whatever else may have made its way up there. Don’t forget to clean the pan under your condensation coils!

Are You Sure It Is a “Humming” Sound?

Sometimes the way we would describe a sound is different from how the professionals would describe it. The following are some other sounds an air conditioning unit might make, and what they could mean. As it’s also difficult to decipher the difference between them or where on the unit it’s coming from.

If you have not yet found the source of your problem, you might want to read through the next bit of helpful information.

  • Buzz? Could it possibly have been a buzzing noise, and not a humming one? A buzzing AC often will point to an electrical issue.
  • Clicking? If you are hearing a clicking noise, we’ll have to take a look at your air conditioner’s relays.
  • Rattle? A rattle can be a sign of something loose within the unit, whether it’s a part that has come undone or foreign material such as debris from a tree.
  • Banging? When a banging sound is coming from your RV AC, you may have a loose part, system imbalance or faulty compressor.
  • Squealing or squeaking? These squeaking noises can be caused by loose elements or the fan and duct system, whereas a squealing type noise can be signs of a fan motor going bad.
  • Screeching or screaming? Turn it off! The professionals advise you to turn off a screeching or screaming air conditioner right away & call your local trusted repair shop. That horrifying noise is loud and annoying for a good reason. It is a warning that something needs serious and immediate attention.

If you’ve come across anything, you’re not sure about, or not comfortable with fixing, take your beloved motorhome to a mechanic and get it into capable hands. You’ll have it back in no time!

Keeping Cool in Your RV If the A/C Goes Down

Looking for ways to keep cool, other than blasting your AC?

  • Wear loose fitting, lightweight clothing can help from overheating.
  • The same goes for bedding. Pay attention to the material of your bedding and density of your mattress for the coolest and most comfortable sleep.
  • Watch your diet and eat in a healthy balanced way to keep your body systems functioning properly and keep your internal temps down!
  • Drink plenty of water to give your body the hydration it needs
  • Ice Packs. Go all out and pack as many ice packs as you can fit into your freezer! Placing them on your pulse points cools you down in an instant. Take one everywhere you go!

Hopefully, these tips will help you identify what that humming noise is – and if it is indeed “humming” you hear. Take a look at this guide to help inform whatever repair decision you or your mechanic will be making.

In the meantime, if that hum grinds to a halt and you’re A/C is down for a bit, follow our tips to keep cool and hydrated until your RV’s air conditioning is back up and running.

Diane Dee

Diane is a lover of all things travel. She and her young family wanted to explore North America from the comfort of their own home so they bought an RV. After fully rehabbing a 1994 Safari Trek, they set out to explore both Canada and the USA.

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