Now that it is winter, one of the necessary RV appliances that you need and must work well is the furnace. There is nothing more disappointing than the moment you turn on your furnace and all you get is cold air. This likely leaves you wondering, “Why does my RV furnace blow cold air?”
Before you give up and check into a hotel, there is some value in troubleshooting. There are several potential causes for your RV furnace fan to run without heat.
If you need heat but are struggling with an RV furnace that blows cold air, we have some thoughts. Follow along with us as we give you some common answers to the question, “Why does my RV furnace blow cold air?”
Why Is My RV Furnace Running But No Heat?
Your RV furnace is a simple appliance. The underlying cause of a furnace that moves air but doesn’t make heat is a problem that may start with the burner or heating element.
When the furnace is not producing heat, start troubleshooting the fuel for the furnace or the electrical components. Some causes are maintenance related. If you are not maintaining your RV furnace properly, this is a good time to start.
How Does an RV Furnace Work?
Most RV furnaces work similarly to the natural gas or propane forced-air systems that are installed in brick-and-stick homes. These systems are comprised of the following components:
- Fuel Source
- Sail Switch
- Control Board
- High-level Switch
To start heating your RV, you first set the thermostat to a temperature higher than the air inside the camper. This triggers the blower motor to turn on. Initially, you may feel the RV furnace blow cold air. This shouldn’t last long, however.
When the blower motor turns fast enough, this prompts the ignitor to light and start burning propane gas. The burning propane creates heat, which is sent to the inside of your RV through ductwork.
10 Reasons Your RV Furnace Might Blow Cold Air
If you turn on the heat only to have your RV furnace blow cold air, this is the time to start troubleshooting. Many problems that would cause the furnace to blow air are fairly easy and quick to fix. If you need heat, here are some potential problems with your RV furnace.
1. Gas Valve Issues
There are two ways that your gas valve can fail. The first is that the valve could be plugged with dust, debris, and other crud. This inhibits the flow of propane through the valve and into the furnace. The other is that the solenoids have stopped working. In this situation, the parts that open the valve no longer work. The valve stays closed, and propane doesn’t get to the furnace.
Before you start, you’ll need to access the gas valve in the furnace. The first step is to check if the valve is obstructed. To clean a plugged-up valve, carefully clean it using a cotton swab, a bit of compressed air, or use a soft brush.
If the valve is clear of debris, try running the system to check the solenoids. When the fan turns on, and you hear a click from the solenoids, but the valve doesn’t open, you’ll smell propane. Therefore, it may be time to replace the valve or the solenoids.
2. Bad Sail Switch
The sail switch is an important safety feature of your RV furnace. It detects whether there is enough power being delivered to the blower motor to operate the RV furnace properly.
If the blower motor is not getting enough power, it will not turn fast enough to trigger the sail switch. When the sail switch is not activated, the burner will not receive propane, and the RV furnace will only blow cold air.
The fix for this problem is simple. You need to check the voltage that your RV or travel trailer battery is putting out. If there isn’t enough power coming from the battery, there are two fixes. First, try charging the battery with shore power. If that doesn’t work, you will need to purchase a new battery.
3. Improper Fuel Source
Your RV heater is designed to run on a specific fuel source, with a specific ignition point. If you are not using the correct fuel, your RV furnace will not be able to ignite the burner.
Make sure that you always use the correct type of fuel for your RV furnace. Also, if your furnace is not working due to an incorrect fuel type, other appliances in your RV will also not work. If your hot water heater, stove and oven, and refrigerator won’t work, then you know that fuel is your problem.
Additionally, make sure that your propane tank is full and turned on. If you are out of propane or didn’t turn on the propane valve, your camper furnace will not be able to function.
4. Low Voltage/Power Issues
Low voltage and power supply issues can cause a host of problems besides making the RV furnace blow cold air. Usually, power problems are caused by a low battery charge or the motorhome not properly connected to the electrical source.
You’ll want to make sure that your RV tool kit includes a voltage meter. You can use this to check the power that is coming to your RV appliances and power outlets. If you are measuring a low voltage, you will need to narrow down the problem.
Check your battery, and battery connections if you are running on the camper battery. If you are using shore power, make sure your camper or travel trailer is properly plugged into the outlet.
We have also seen RV surge protectors fail, which prevents the shore power from reaching your RV. If your surge protector lights aren’t on, it may have malfunctioned.
5. Dirty Connections
Dirt and corrosion can wreak havoc on all sorts of connections in your camper’s electrical and fuel systems. If electrical connections are dirty or corroded, they cannot make solid contact, and you may experience low voltage issues.
If your gas line connections are dirty, they may not seal correctly, and you could be leaking gas or not have enough pressure to push propane into your furnace.
Check all the electrical and gas connection points to your RV. If you notice that they are dirty or corroded, you can simply clean the connection points, Then reconnect your battery, shore power, or propane tank. It is also a good idea to add cleaning these connections to your periodic maintenance tasks.
6. Problems with the Ignitor
The ignitor of your RV furnace is one of those parts that can and will eventually fail. When it does, the RV furnace will most certainly blast cold air. If you can hear the clicks from the ignitor, but the furnace never heats, you can bet the ignitor has failed.
Unfortunately, there is not much you can do if the furnace ignitor has failed. You can try cleaning the ends of the wires. Sometimes they get gunked up and do not spark well. If this doesn’t work, you will be stuck replacing the igniter.
Only attempt this repair if you feel confident doing this kind of work on your RV. It is not too difficult of a process. However, an RV technician can do this replacement quickly and at a minimal cost.
7. Broken Thermostat
Your thermostat is a good place to start when troubleshooting. Two possible problems can cause the thermostat to fail. Either it is broken or dirty. These are the two most common problems with your thermostat.
First, start by trying to clean the inside of the thermostat with a bit of compressed air. If blowing out the dust doesn’t help, your next option is to replace the thermostat.
8. Tripped Circuit Breaker Or Fuse
If you are noticing that your RV furnace is blowing cold air, you may want to check and see if a circuit breaker has tripped. This is caused when an electrical system or part pulls too much energy. It happens when there is something faulty in the appliance or maybe a surge in your shore power.
Start by switching the circuit breaker back on. If you are dealing with a power surge, this may solve your problem.
If a part of your RV furnace is not functioning correctly, it will continue to cause the breaker to trip. In this case, you’ll want to use your voltage meter to track down the culprit. This fix may require you to replace or repair all or part of your RV furnace.
9. Dirty Air Intake
If your air intake gets filled up with dirt and debris, it could prevent the gas furnace from getting enough oxygen. Without enough oxygen, the burners will not light. If you have a hydronic heater, the dirty intake will limit the airflow to the blowers when the system needs to use diesel to heat the hot water quickly.
If this is the cause of your problem, the easy fix is to clean out the intake and place screening over the air openings to minimize insects and dirt from getting inside. Your RV manufacturer likely has a recommended procedure. The same is true for the exhaust.
10. Carbon Buildup on Diesel Heater
If your furnace runs on diesel, you need to make sure that the input for the furnace is far enough from the output of the furnace. The great thing about diesel is that it burns slower than other fuels. But it is dirty. If the air intake for the furnace is too close to the furnace output, it can suck residual carbon back into the heater.
Ensure that your furnace intake isn’t too close to the output venting. If they are right next to each other, work with your local RV repair shop to have your system renovated to move the output further from the heater input. Make sure to have the carbon cleaned from the furnace, as well.
Can You Fix a Malfunctioning Heater Yourself?
Depending on the malfunction, many problems that cause your RV furnace to blow cold air are easy to fix. Things like replacing or cleaning the filters, replacing a broken thermostat, and making sure you have plenty of the correct fuel are perfect DIY fixes.
Other fixes are more complicated. If you are not comfortable with electrical work or dissecting the venting system of your RV, you will want to enlist the help of a qualified RV repair technician.
Can You Simply Reset Your RV Furnace?
Sometimes, your furnace may just be confused. Before you start tearing apart your RV furnace to resolve the cold air issue, try turning it off completely. This will reset the furnace.
Sometimes, this helps; other times, it does not. If this does not alleviate the problem, you can deduce there could be a larger issue with your RV furnace.
Final Thoughts on Fixing an RV Furnace That Blows Cold Air
“Why does my RV furnace blow cold air?” This is a common question from many RV owners during cold weather. If you are facing this quandary, there are several things to check before you run out and replace your RV furnace.
To avoid these problems when you need your RV furnace the most, it is always a good idea to test it in the summer. Doing this helps you discover if there are any problems before the fall camping season when the night temperatures start to drop.
Many of the problems that make an RV furnace blow cold air are easy to diagnose, and many can be resolved with simple, DIY fixes. We have offered some of the most common problems and solutions. If these do not work, you know it is time to find a warm hotel and a friendly RV repair shop.
About the Author:
Jason Gass is a full-time freelance writer and part-time RVer whose goal is to share great stories around a campfire with good friends.
When he’s not working, he spends most of his time camping, searching for the best breweries, and road-tripping in his teardrop trailer with his wife, daughter, and two dogs.