Is your RV air conditioner abnormally loud or noisy? RV air conditioners are rather infamous for being irritatingly noisy in general, but if you hear a rattling, buzzing, humming, or other strange sound, then that’s your appliance sounding the warning bell. And remember: An RV air conditioner with low refrigerant generally cannot be recharged.

As I said, RV air conditioners make a lot of “whooshing” noise in general. They move a lot of air through small ducts and obstructed plenums. That’s one reason why many RV owners prefer a fully ducted air conditioner, which is much quieter because all that raging airflow is quietly contained inside the ceiling itself. 

But as for these other noises … they are not normal. Most are due to a mechanical issue, although electrical issues can sometimes manifest as aberrant sounds. DO NOT CONTINUE TO OPERATE an air conditioner that sounds like it ate a breakfast of ball bearings or is trying to hum a high C. Noises are symptoms only. Treat the cause, not the symptom. 

Let’s run through my Top 10 reasons why your RV air conditioner might be making a weird or strange noise. 

Broken Fan

A broken fan will be out of balance. That will decrease airflow, cause noisy turbulence, wear out bearings, and cause vibration. A broken or chipped fan blade can sound like a mini jet turbine engine! 

Your A/C has two fans:

• A blower fan that blows hot air across the condenser
• A cooling fan that blows cold air across the evaporator

Either fan can break, so check both. To replace the fan usually requires removing the air conditioner motor as well. You’ll need to mount the roof, remove the shroud, and possibly remove the evaporator housing as well. Bring tools! And while you’re at it, why not clean the evaporator coils at the same time?

Trespassing Mouse 

If you turn on your air conditioner on Fan or Cool mode only to hear a rattling or thundering noise, it’s quite possible a rodent has constructed a condo inside your blower fan. Anything inside is now probably dead, but the debris is still rattling around. You’ll need to get on the roof, remove the A/C shroud, and clean out the leftovers. In many cases, the fan wheel will also be broken, so be prepared to replace that, too.

Some particularly huge mice or chipmunk nests can actually stop a fan from spinning at all! If power is left on, this will burn up the motor and require a replacement. 

Damaged Compressor Mounts

The compressor sits on rubber anti-vibration bushings to reduce vibration. If those mounts break or wear out, then the compressor will transmit its vibrations to the sheet metal pan. That’s usually pretty loud and rattly! You can replace these bushings to reduce the sound. This isn’t a common occurrence, though, and it’s more prevalent on older air conditioners. 

Here’s an easy troubleshooting tip: Can you hear the noise in Fan-only mode? If so, is it also present in Cooling and/or Heat Pump modes? A noise that’s only present in Cool/Heat Pump mode could be more indicative of a compressor problem than a motor.

Dirty Power

“Dirty” power could refer to anything from high frequency, under-voltage, over-voltage, harmonic distortion, or a myriad of other electrical waveform issues. Some of these electrical problems will manifest buzzing or vibrating noises coming from control boards, relays, or motors. 

Most RV air conditioners are rated for 115/120/125 volts alternating current electricity at 60 Hz. Any deviation can cause problems. In particular, voltages under 108 or above 130 can quite literally “sound the alarm.” Grab a multimeter and test your power pedestal if you’re unsure.

If you’re running your rig on an old generator, take this issue seriously! A generator with a bad governor, voltage regulator, or other issue can output horrific electricity. Appliances don’t like that, and you risk letting out the magic smoke. 

>>> READ MORE: RV Air Conditioner Not Blowing Cold Air? 5 Easy Troubleshooting Tips (No Multimeter Required)

Worn-Out Motor Bearings

Most RV air conditioners have a single motor that spins both the evaporator and the condenser fans simultaneously. A few models have dual motors, with one motor for each fan blade. Because these motor shafts spin, they have bearings.

By and large, most RV air conditioner motors do not have serviceable or replaceable bearings. Bearings come in many types, with sleeve and ball bearings being two of the most common. Personally, I’ve never seen an air conditioner motor that had oil ports for serviceable bearings, although that’s not to say they don’t exist anywhere.

Bearings typically go bad from either neglect (lack of use) or wear n’ tear (too much use). Bad bearings can screech, whine, rattle, or even seize completely. The OEMs will tell you to replace the motor. And they’re probably right.

In a pinch, sometimes, you can use a non-detergent lubricating oil in hopes it will seep into the old bearings. You can either coat the shaft and spin the motor by hand, try injecting it between the sleeve and shaft with a hypodermic syringe, or even completely disassemble the motor castings. The YouTube grapevine suggests 3-In-1 or even turbine oil. Try this repair at your own risk – it’s not sanctioned, and it may or may not work!