If you’re reading this guide to troubleshooting your RV air conditioner, I’m guessing something is wrong. So I’ll dispense with my usual hilariously clever introduction. Let’s get our hands dirty.
But first, without any ado, here are the three things I want you to know about troubleshooting an RV air conditioner:
- Unplug your RV from any electrical source before working on the air conditioner to avoid electrical shock. Stay alive!
- Many RV air conditioner troubleshooting problems can be solved by simply maintaining and cleaning your air conditioner! Replace the air filter, clean the condenser coils, clean the evaporator coils, and (if required) lubricate the motor. Boom.
- Start with the simplest solutions. Check your power supply and thermostat before performing invasive surgery on your air conditioner.
- If the problem has anything to do with the compressor or refrigerant copper tubing, it’s probably cheaper to replace the entire air conditioner than hire an HVAC technician to fix it. Thankfully, installing an air conditioner (on your own) is a lot easier than fixing one!
Table of Contents
RV Air Conditioner Won’t Turn On!
If you press the On/Off button and nothing happens, nothing whatsoever, the problem is most likely electrical, not mechanical.
Check Power Supply
You need to confirm that you have adequate and safe power. If plugged into shore power, use an EMS surge protector to scan for codes. A low-voltage brownout condition could cause the air conditioner to not turn on.
If you’re running off an inverter or generator, check those power sources, too. In particular, confirm the transfer switch is working!
Inspect the Converter and Circuit Breakers
If there’s zero power at the unit – no lights, no sound, no buzzing – then start at the converter panelboard. Check if the circuit breaker has tripped. If so, reset the breaker.
If there’s power at the converter and the circuit breaker isn’t tripped or faulty, then you likely have a ground or short somewhere on your circuit. This can be caused by a wayward screw that’s pierced into a wire. Another common cause is a loose connection, such as a loose ferrule crimp or loose wire nut.
Tracking down a short in a bad circuit takes time and expertise. Have a multimeter and know how to use it! Otherwise, call for help.
(Your air conditioner runs on 110VAC power, not 12VDC, so a blown fuse shouldn’t stop your A/C from turning on. It could affect the thermostat, but that’s for the next paragraph!)
A Faulty Thermostat
If there’s power at the unit but the air conditioner won’t kick on, there’s a good chance the thermostat is the appliance to blame. Most thermostats are wall-mounted, so you can easily check if your thermostat has power to it. If not, go to the converter fuse panel and check for blown fuses (since your thermostat runs on 12V power).
If the thermostat itself is bad, you’re better off buying a new one. They are easy to replace – just take a picture of which wire goes where!
RV Air Conditioner Won’t Run!
If you’re getting power to the unit but nothing mechanical is working, it’s likely a problem within the air conditioner itself.
Thermostat Too High
Hey, everyone has their own blonde moments! Did you make sure your thermostat is A) turned on and B) set low enough for the air conditioner to kick on?
Check the Error Code
Most RV air conditioners will blink a fault code when there is a detected issue. Check your Owner’s Manual for the fault code key. Common causes include:
- High-pressure switch: If your A/C senses excessive pressure in the high side of the refrigerant lines, it won’t operate. You need professional help.
- Overheating: In extreme weather, an air conditioner won’t work. Many air conditioners have a safety sensor around 130 degrees Fahrenheit. You can reduce the temperature by parking in the shade, using your window/shades reflectors, ventilating any superheated interior air, and keeping your roof clean.
- Bad capacitors: If the run or start capacitor has gone bad, you’ll often hear a humming, but nothing will turn over.
The Air Conditioner Won’t Stop Running
If your air conditioner won’t stop running, a bad circuit board or bad thermostat is probably to blame.
Installing a new wall-mounted thermostat is easy and cheap. Feel free to try it out.
Installing a new circuit board isn’t always so easy. Call for help.
Air Conditioner Keeps Tripping the Circuit Breaker
Too Much Startup Power
Air conditioners require much more power at startup than during operation! Most power supplies are designed to withstand these temporary surges, but some simply can’t handle the peak wattage. That’s why you can’t run an RV air conditioner on battery power alone.
If you’re running other 120V appliances such as a microwave, refrigerator or kitchen appliance, turn them off. Turn on your air conditioner first, then your fridge, microwave, kitchen gadget, etc., going from largest to smallest appliance.
If that still doesn’t do it, then you need more power!
Of course, you probably don’t have more power available. Nor do you want to shell out the money for a replacement high-efficiency air conditioner.
Perhaps you should look into a Soft Start, which is a pretty cool gadget. It’s a capacitor that basically stores energy for a few seconds, and then releases it all at once to the air conditioner. That way, the Soft Start takes the brunt of the peak startup power, not the power source.
Too Much Continuous Power
If you’re trying to run two 13.5k or 15k BTU air conditioners with a 30A connection or a portable generator, you’ll often encounter this problem. There just isn’t enough juice to go around!
If your RV air conditioner starts but shuts off in 30 seconds to 5 minutes, you might be drawing more amps than your circuit can handle.
If you’re running other 120V appliances such as a microwave, refrigerator or kitchen appliance, turn them off. Turn on the air conditioner first. Once it’s running reliably, turn on your other appliances, moving from smallest to largest.
Low Voltage at Power Pedestal
As I’ve talked about before, low voltage causes your RV to draw more amps. The more amps, the more likely you are to trip a breaker. Check the voltage from your power source with a smart surge protector.
This problem often presents itself around 6:00 p.m. on a hot, sticky summer night at a campground, just when everyone else is trying to run their air conditioner at the same time!
Air Conditioner Not Blowing Cold Air
An operating compressor should make some noise and feel warm to the touch. A broken compressor won’t circulate refrigerant, and nothing will work.
Crazy Hot Outside
An air conditioner can only work if it’s able to superheat the refrigerant so it’s hotter than the outside air. Some air conditioners may simply not work if the temperature outside exceeds 110-115 degrees Fahrenheit.
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
If either fan is broken, the A/C likely won’t blow cold air. The problem is likely either a seized motor bearing or a shattered fan blade.
One symptom of a broken (or dying) fan is if the fan can only operate at a single speed.
Dirty Air Filter
If your air conditioner is not cooling your RV as well as it used to, the first thing you should check is the air filter. A dirty air filter can restrict airflow and cause your air conditioner to work harder than it needs to. Replacing a dirty air filter with a clean one can improve your air conditioner’s efficiency and cool your home-on-wheels better.
Most manufacturers recommend you clean your air filter every two weeks of operation! Use a handheld vacuum to suck out the dust and grime.
Damaged or Dirty Fins
The cooling and heating fins on the inside and outside of your air conditioner are what allow heat to flow. Dirty or damaged fins – bent, folded, flattened – reduce the ability of your air conditioner to transfer heat.
- If your cooling fins (condenser) are damaged, then the air blowing across them can’t pick up as much cool air.
- If your heating fins (evaporator) are damaged, then the air blowing across them can’t pick up as much heat, which means the refrigerant stays too warm.
Keep your fins straight and clean! If your fins are damaged, you can buy a fin comb to straighten them out.
Low Refrigerant Level
This is the cause everyone suspects, but it’s rarely the case!
An RV air conditioner has a sealed refrigerant system. No refrigerant should be escaping. But if you have a leak somewhere in the system, then low refrigerant could cause frost on the cooling coils.
Signs of low refrigerant include warm air blowing and frost on the cooling coils.
If you suspect a refrigerant leak, ake off the interior shroud and exterior cover to check for leaks. Refrigerants have different colors:
- R-22 (Freon): Light Green
- R-410a: Light Pink/Rose
- R-134a: Light Blue
- R-23: Light Blue Gray
… but in a small leak, it’s hard to tell the difference. They all look thin and oily.
Unfortunately, even if you have a leak, there’s not much you can do about it. Most RV air conditioners have sealed, pre-charged refrigerant lines. There are no high-pressure and low-pressure ports to take a pressure reading or add refrigerant, like in a car. You’ll usually have to buy a new air conditioner or risk MacGyvering a solution.
Air Conditioner Is Loud and Noisy
Compressor Mounts Damaged
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.
Some types of blower motors need to be regularly oiled and serviced. Check your Owner’s Manual for information. If so, most units use SAE 20 non-detergent type oil, available at most HVAC supply stores.
Worn-Out Motor Bearings
An old, worn-out motor might have junk bearings. The little round balls inside the bearings have become pitted or deformed. If you’re lucky, you might be able to replace or service just the bearings, but you’ll probably have to replace the entire motor. Most RV air conditioners use sleeved-bearing motors, which cannot be easily disassembled and rebuilt.
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 and make noise, so check both.
Water Leaking From the Air Conditioner
If you’re noticing a trickle of water leak from the air conditioner outside your RV onto your roof, that’s normal. All air conditioners remove water from the air, and that water has to go somewhere! Ergo, it gets dumped onto your RV roof.
But if there’s a puddle of water beneath the air conditioner inside your camper, then you definitely have a problem.
There should be a hard foam rubber gasket between your air conditioner and your roof. If that gasket gets old and damaged, or if a gap develops, then water could leak from your roof into your interior!
You might notice this issue either while running your air conditioner for extended periods of time or after a hard rainstorm.
You can often fix a leaking gasket simply by tightening the mounting bolts. If that doesn’t do it, you’ll need to reinstall the air conditioner with a new gasket.
Sediment, grime, leaves, or mouse nesting can get stuck in the condensate drain hole. Remove the top from the air conditioner and check for a clog first! If you’re not sure where the water runs, fill up a water bottle and slowly pour the liquid into the drain pan. Watch where it goes!
I have seen water dripping inside an RV from the air conditioner because loose wires laid against the cooling coils. Rather than dripping into the pan, the water took a detour down the wires and into the interior!
Frost on Evaporator Coil
If you have excessive frost on the evaporator coil – often caused by damaged fins or low refrigerant – then the water could be building up and draining through the cold air return or supply vents
To melt ice on the evaporator coils, just run your air conditioner on Fan Only mode until they’re defrosted.
RV Air Conditioner Causes Condensation Inside
What if you wake up to tiny droplets of water all over your RV ceiling?
Cold air can hold less moisture. That’s just a fact of science. So if you cool down hot, humid air, the excess water has to go somewhere. It condenses onto surrounding surfaces, usually the coldest ones. In an RV, that often means you’ll get water condensation on your windows and skylights. In severe cases, you might get condensation everywhere!
Sometimes, excessive condensation is caused by running an air conditioner that’s too big for the space. A super-powerful air conditioner will cool down the air before it’s had a chance to remove the moisture. But in RVs, this is rare, because most air conditioners err on the side of being too small!
Most of the time, I’ve seen this issue when travelers camp in a humid climate, run their air conditioners at night, wake up in the morning, and see little water droplets on their ceilings. That’s because outside air has leaked inside the camper (morning air is usually extra humid). When confronted with the 65-degree Arctic oasis inside, that atmospheric moisture condenses on whatever’s closest.
There’s not one solution to this problem, but here are a few ideas:
- Draft-seal your RV windows and doors.
- Don’t set your air conditioner so cold.
- Run your roof vent as a ceiling fan.
- Use desiccants.
P.S. If you’re using a so-called “portable RV air conditioner,” then you’re creating this problem for yourself!
The Air Conditioner Stinks!
If your air conditioner stinks, check your air filter first.
If that’s clean, then I’d wager you have dead mice or dead birds lodged somewhere in your air conditioner. Eww.