Troubleshooting Your RV Air Conditioner: A Step-by-Step Guide

There's nothing worse than a hot summer day, an RV full of family and friends, and an air conditioner that's just not doing its job. Sound familiar? Well, don't worry! Whether you're dealing with error codes, lackluster cooling, environmental problems, or just want to make sure everything is running smoothly, this guide will walk you through the steps to troubleshoot your RV air conditioner.

In this guide, we’ll use a Furrion air conditioner as our example, but the principles can be carried over to many different systems.

In this blog, we’ll look at the following areas:

• Understanding AC error codes
• Testing operating temperatures
• Testing for low refrigerant
• Checking for proper installation
• Considering user errors and environmental factors
• Verifying your control box is working

First things first, let's talk about error codes. These are your AC's way of telling you something isn't quite right.

Error codes are typically marked by different numbers, such as E1, E2, E3, etc. Different brands of RV air conditioners, including Furrion air conditioners, use codes like this, but the codes don’t always mean the same thing across different brands. So, don’t assume all AC units work the same way!

Refer to the instructions of your specific manufacturer when assessing error codes.

Indoor Temperature Sensor Failure

This error indicates a failure of the indoor temperature sensor and is indicated on Furrion ACs by an “E1”. If you see this error on your unit, it can mean one of two things. 1) If the indoor temp sensor is located in the return air, it means you’ll need a new control box. 2) If the indoor sensor is on the thermostat, the thermostat needs replacing.

Evaporator Sensor Failure

This means your evaporator or freeze sensor has become an open circuit. If you get this error, you can replace the sensor, but first, check to see if it’s just a loose connection. A loose wiring connection can cause an open circuit in your system, and this can trigger the evaporator error.

Condenser Sensor Failure

This error refers to the condenser sensor (most Furrion air conditioners don’t have this ). If you see this error code, it’s likely due to an accidentally turned-on heat pump dip switch. Just switch it off, and you should be good to go.

Outdoor Sensor Failure

This error code means that the outdoor temperature sensor on your RV AC system is out of order. It will cause the entire system to shut down, but fortunately, this sensor can also be replaced fairly easily to get your AC unit back in good working order.

Loss of Communication

This error code (indicated by an “E3” on Furrion ACs) points to a loss of communication between the control box and the thermostat. Check the A and B communication wires — either they’re wired incorrectly, or there’s some damage in the line.

Low Voltage

This error is for low DC voltage, indicating that the voltage has dropped below 10 volts. Check your RV batteries or other DC power source and the connections to fix this problem.

Now, let's dive into the most common problem —  your RV AC isn't cooling. There’s nothing worse than an air conditioner blowing warm air on a hot day. Typically, for a non-cooling AC, the issue is one of three possibilities: either it’s an issue with the unit itself (something performance related), the installation, or perhaps the way you're using it.

Let's start with one of the most common sources of RV air conditioner problems: unit performance. To test your air conditioner’s performance, begin by running it for 15 minutes. This helps get the unit primed and in its normal working conditions.

Then, we’re going to take some measurements for temperature and amperage. Have your thermometer and multimeter ready! Also, we’ll be climbing onto the roof of the RV, so use caution. If you’re not comfortable with the following steps, it’s okay to ask for professional help!

First, measure the intake temperature at the return air grille where air is going into the AC from the outside. Next, measure the discharge temperature at the closest vent inside your RV.

Ideally, the difference between the air going in and the air coming out should be about 24 to 30 degrees. If it’s less, you might have a low refrigerant charge; that is, your AC might be low on refrigerant and will need to be recharged.

Now let’s check the operating amperage of your unit. Start at the compressor wire (this wire is blue on our Furrion example). Clamp your multimeter onto the wire to measure the amp draw. Then, take another temperature reading, this time outside near the AC. We’re looking for the ambient temperature of the air around your unit.

Next, we want to do a quick comparison of the compressor wire amp draw to the unit’s RLA. RLA stands for Rated Load Amps. It’s basically a spec on your AC that indicates the maximum amount of amps the unit should pull at its maximum load (hence why we ran the unit for 15 minutes first!). You should be able to find the RLA for your unit printed on its data tag (on Furrion units, remove the shroud and look for the data tag on the inside metal panel). For many RV air conditioners, including Furrion units, the RLA is calculated at 95 degrees Fahrenheit, 50% humidity, and 115 volts AC. Consult the owner’s manual for recommendations from the manufacturer on your specific unit.

Let’s compare the compressor wire amp reading with the RLA, taking into account the ambient temperature around the AC unit. First, use the ambient temperature and subtract it from the RLA temperature rating —  again, for most RV ACs, this is 95 degrees. For every 10 degrees of difference, the expected amperage on the compressor wire should be adjusted by one amp. In other words, if it’s 105 degrees outside on your RV roof, the amp draw should go up by one. If it’s 85 degrees on the roof, the amp draw should go down by one.

Expected amp adjustment = (Ambient temperature - RLA temperature rating) / 10

Expected amps = RLA amp rating + / - expected amp adjustment

If the amp reading on your compressor wire doesn’t match up with the expected amps, the likely cause is that your AC doesn’t have enough refrigerant. More on this in a moment.

Let’s say we measure the temperature on the roof near our AC to be 80 degrees. Comparing this to our RLA temperature (95 degrees), we get a difference of 15 degrees.

Remember…

• For every +10-degree difference = +1 amp.
• For every -10-degree difference = -1 amp.

With a drop of 15 degrees, our expected amps should drop by around 1.5 amps.

Expected amp adjustment = (80 degrees - 95 degrees) / 10 = 1.5

Let’s say in our example that the AC unit’s data tag indicates an RLA rating of 12.6 amps. So, our expected amp reading from the compressor wire should be about 11.1 amps. And according to our temperature reading and adjustment equation above, it is!

Expected amps = 12.6 - 1.5 = 11.1

If you test your RV AC using the formula above and you find that the compressor wire amperage draw is too low or that the temperature difference between your AC intake and output is too low, it means that your unit doesn’t have enough refrigerant. There isn’t enough refrigerant in the system to place the proper resistance on your compressor. The solution is to add refrigerant, but you also want to make sure your compressor isn’t leaking. If it is, you may need to replace it.

The next thing to troubleshoot on your RV air conditioner is that it was installed properly. Here are some things to look out for.

Leaks

A leaky AC system is an inefficient system. Unchecked leaks can actually cause the system to freeze up. Ensure there's no air leaking between the return and discharge sections. Leaks can be caused by poorly installed heat tape and PE foam. If you notice gaps along the edges or dividers, use foil tape to seal them up.

Sensor Location

RV air conditioners operate using different sensors to detect temperatures within your RV. If these sensors are not in the correct locations, it can cause the system to malfunction. In many cases, this is indicated by frequent on-off cycling. Verify that your sensors are installed correctly and that all connections are secure.

Coils

Finally, inspect the coils. The coils on both the evaporator and condenser must be clean and undamaged to ensure a well-functioning unit.

Another common source of RV air conditioner problems is user error as well as environmental conditions. Two simple questions to ask are, are you using your RV AC correctly, and is the environment around your AC affecting its performance?

1. Direct sunlight or a dark-colored exterior on your RV can make it harder for your AC to keep things cool. Consider parking in a shadier spot if your air conditioner is struggling.
2. Make sure none of your vents are blocked or covered. Proper airflow is crucial for efficient cooling, and air must be allowed to distribute through the RV to regulate its interior temperature. If a vent is blocked, remove the blockage before proceeding with operation.
3. Keep an eye on humidity levels and fan speed. If the humidity is high, the AC will struggle to remove moisture from the air. Likewise, if the fan speed isn’t set high enough, moisture can become a problem.
4. Limit how often you open and close your RV’s door, as this introduces heat and humidity. If you enter and exit frequently while your RV AC is trying to work, you’re making the work that much harder.
5. Remember, too many heat-producing appliances (or even too many people) inside the RV can overload your AC’s cooling capacity. The average human produces 7,200 BTUs of heat per day! If it’s a hot day and your AC is already working hard, consider a cold lunch or dining outside instead of firing up the cooktop.

Lastly, if all else checks out — the amperage draw is right, the unit is installed correctly, and you’re within recommended operating parameters —  ensure the control box is functioning properly.
Let’s get out the multimeter again. You can also use a test light for this step.

What we’re looking for in this troubleshooting procedure is continuity in the wiring connections; that is, we want to make sure each function of the AC unit is getting the proper charge through the wiring harness.

We’re going to test each wiring connection point against the neutral wire (white on our Furrion example). Unplug the control box and place one lead of the multimeter in the neutral wire port, and the other lead into each function below to check for continuity (don’t just check for voltage!).

Here’s what our Furrion AC example looks like:

• Voltage check - 115V hot (black) to neutral (white)
• Compressor check - Compressor wire (blue) to neutral (white) = 115V DC
  (Note, select cool and lower setpoint temperature below room temperature)
• Select Low Fan on controller - Low Fan wire (red) to neutral (white) = 115V DC
• Select Medium Fan on controller - Medium Fan wire (red) to neutral (white) = 115V DC
• Select High Fan on controller - High Fan wire (black) to neutral (white) = 115V DC
  (Make sure the fan is not selected on Auto!)

Troubleshooting your RV air conditioner doesn’t have to be intimidating. With this guide, you can diagnose and address common issues, ensuring your AC keeps you cool all summer long. And remember, you’re not alone in this. We not only offer a wide range of technical resources on our ACs, we also have an extensive dealer / installer network and a committed customer service team ready to help.

Disclaimer: These photographs, recommendations, and approximations are intended for demonstration purposes only and do not reflect the specifications of any particular AC unit, recreational vehicle, or trailer. Always consult the manufacturer’s Owner's Manual.