Skip to Content

RV Furnace Not Working? Let’s Troubleshoot!

RV Furnace Not Working? Let’s Troubleshoot!

If your RV furnace isn’t working, there are a number of possibilities as to the reasons why. Depending on the symptoms your furnace is experiencing, you can troubleshoot a non-working RV furnace on your own. This post aims to help you with that process.

We’re going to be focusing here on the most typical RV furnace, the propane furnace. Hydronic heat (HydroHot, AquaHot, Oasis) is a different breed of RV furnace, and we’re not covering those here. This post assumes you’ve got a typical propane RV furnace.

An important safety note: Your RV furnace uses both propane and electricity, both of which can potentially pose a danger. If you’re not comfortable dealing with propane or electricity, call in a professional for anything other than the most basic of these troubleshooting ideas.

Let’s get to it!

How Does an RV Furnace Work?

An RV propane furnace is a forced-hot-air system that requires a thermostat, a control board, a relay, a blower motor, sail switch, high-level switch, ignitor, and some ductwork.

A traditional RV propane furnace uses both propane and electricity (12V DC from the battery(ies) in your RV). The propane burns to create hot air while the electricity powers the electronics & circuits (in both the furnace and thermostat) and run the fans.

To make the system work, you set the thermostat higher than the RV’s current inside air temperature, which triggers the furnace to activate the blower motor. Ultimately, if the system functions correctly, the propane ignites, creating hot air that’s distributed throughout the RV through the ducts.

That’s the nutshell version. For a closer look at each of the steps involved in the operation of an RV propane furnace and the parts required for it, see our detailed post explaining how an RV propane furnace works.

What Are RV Furnace Diagnostic Codes?

Furnace diagnostic codes can assist you in determining if something has gone awry, keeping the system from working properly.

Newer RV furnaces will have a diagnostic light. The circuit board sends signals that illuminate the diagnostic light with a number of flashes representing a particular code (similar to Morse code).

A chart in the owner’s manual (or sometimes on a sticker on the furnace itself) identifies the meaning of each code, allowing you to interpret the information offered by the diagnostic lights.

So, you’ll note the number of flashes from the light, and then look up the meaning using the corresponding code in your owner’s manual or on the sticker on the furnace. With that information, you’re on your way to fixing the problem.

Typical RV Furnace Wiring Diagram

To get started with your troubleshooting, it will be helpful to understand how your furnace is wired. This is a diagram of a typical Atwood/Dometic RV furnace. The diagram for a Suburban RV furnace would be similar.

Is your RV furnace not working? Check out the wiring schematic for an Atwood/Dometic RV furnace. (Diagram and photo credit: Atwood/Dometic)

Wiring diagram of an Atwood/Dometic RV propane furnace. The schematic for a Suburban furnace would be similar.

The Most Common Reasons Why an RV Furnace Is Not Working and How to Troubleshoot Them

There could be a number of reasons why your furnace doesn’t produce heat when you turn up the thermostat in your RV.

Let’s take a look at the most common issues and how to troubleshoot them.

You Turn Up Your RV’s Thermostat and Nothing Happens

When you turn up your RV’s thermostat, within a few seconds you should hear a fan kick on. If you turn up your RV’s thermostat and nothing happens at all, then your fan/blower motor isn’t starting. A non-functioning fan/blower motor could have a number of causes.

Inadequate Power Supply

A traditional RV propane furnace requires a strong 12V power supply for various furnace components to operate. If your furnace doesn’t kick on at all (meaning you never even hear the fan come on) this could be due to low battery voltage.

The first thing you’ll want to do is check your 12V power supply to make sure you have adequate 12V power to run the furnace. If you have a dead house battery, for example, the furnace won’t be able to function.

Confirm that you have a strong 12V power supply coming from your RV’s batteries, and then check the connections along the wire running from the thermostat to the furnace’s circuit board.

You can use a multimeter like this one to check for adequate 12V power.

Sale
AstroAI Digital Clamp Meter Multimeter 2000 Counts Amp Voltage Tester Auto-ranging with AC/DC Voltage, AC Current, Resistance, Capacitance, Continuity, Live Wire Test, Non-contact Voltage Detection
  • Versatile Digital Clamp Meter: Accurately measures AC Current (DO NOT MEASURE DC CURRENT)! AC/DC Voltage, Capacitance, Resistance, Diode Continuity...
  • Large Jaw Opening: The jaw opening measures AC current in a conductor without touching or interrupting the circuit. Its slim and compact size makes it...

Relay for the Blower Motor is Bad

Another reason why your furnace fan may not be kicking on involves the relay on the circuit board. If the relay isn’t opening, the blower/fan can’t start. In this case, you can troubleshoot by testing the relay.

To do this, you’ll bypass the relay to see if the fan will run on the direct power from the battery. If the fan functions using direct power, then you know that the fan is good and the problem is likely to be the relay.

However, if the fan doesn’t run on battery power, this indicates that your relay is likely okay but the fan itself is problematic (or stuck… if it’s been a while since you last used your furnace, it could be seized from rust).

Note that if you’re hearing a squealing sound from your RV furnace, this is likely a blower motor that needs to be replaced.

Here’s a look at the components of the blower – the motor, combustion wheel, and blower wheel:

Atwood/Dometic blower motor:

Sale
Atwood 37697 Hydro Flame Replacement Motor
  • RELIABLE - The Atwood 37697 is a The Atwood 37697 is a Hydro Flame replacement motor for Atwood furnaces.
  • COMPATIBILE - Works with furnace models 85-IV 25, 85-IV 31.

Atwood/Dometic combustion wheel:

Sale
Atwood 33128 Hydro Flame Combustion Wheel
  • FURNACE PART - Hydro Flame Combustion Wheel
  • TRUSTED BRAND - One of hundreds of Atwood products for furnace solutions.

Atwood/Dometic blower wheel:

Sale
Atwood 33126 Blower Wheel
  • HIGH-QUALITY BLOWER WHEEL – Featuring 40 blades and counter-clockwise rotation, the Dometic Atwood Blower Wheel is the ideal replacement for your...
  • COMPATIBLE WITH – 8516-III, 8516-IV 8520-III, 8520-IV, 8525-III, 8525-IV, 8531-III, 8531-IV, 8535-III, 8535-IV, AFMD16, AFMD20, AFMD25, AFMD30,...

My RV Furnace Fan Runs But There’s No Heat

If you turn up your RV’s thermostat and in a few seconds you hear the fan kick on but it’s blowing cold air that doesn’t warm up, you could have any one of a number of problems, most of which you may be able to address yourself.

Fuel (Propane) Source

The number one reason behind a furnace that’s not supplying heat is your fuel source. The most obvious issue, and the first one to check, is your propane supply. Make sure you have adequate propane to run your RV’s furnace.

If you don’t have a gauge handy, you can check your tank level without a gauge.

Or Peter can walk you through the process in our YouTube video on how to check your propane tank without a gauge:

You’ll also want to make sure your propane tank valve is open (did you close it when you stored your RV?), and your onboard propane regulator hasn’t failed or clogged. See our post for more information on RV propane regulators.

Sail Switch Failure

Another common reason for an RV furnace that’s running, but isn’t producing heat, is the failure of the sail switch to open. The sail switch is one of two safety switches in your RV furnace, and if it doesn’t open your RV furnace won’t produce heat.

The sail switch itself can fail over time, or it can simply be clogged with debris such as dust, pet hair, insect nests, or rust. In some cases, the sail switch may be able to be blown clean and continue to work properly. In others, it will need to be replaced.

You can find detailed information on the sail switch in our post: “What Is an RV Furnace Sail Switch?

Here’s an example of a sail switch:

Atwood 36680 Sail Switch
  • BUILT FOR RV - Sail switch specifically designed for use with RV's and Campers.
  • FULLY GUARANTEED - Includes manufacturer warranty.

Bad Gas Valve

If your RV’s furnace fan runs but the furnace isn’t producing heat, you may also have a bad gas valve.

Take a seat near the exhaust port of your RV’s furnace while someone else works the thermostat to trigger the furnace to come on. When you fire up your RV furnace you should hear the fan turn on, then the solenoid should make a clicking sound. Next you should hear a rapid ticking sound (the ignitor), and then you should smell propane gas.

However, if your RV furnace’s fan turns on and you hear the click of the solenoids and then the rapid ticking sound, but you do NOT smell propane, you’ve likely got an issue with your furnace’s gas valve.

Here’s an example of a gas valve for a Suburban RV furnace:

Sale
Suburban 161122 Gas Valve
  • Rig Rite 12/24 Volt Marine Circuit Breaker w/ Auto Reset - 40 Amp

Failure of the Ignitor

Next in line in the furnace lighting process is the ignitor, so let’s troubleshoot that element.

Once again, seated at the exhaust port of your RV’s furnace, listen carefully to what happens when the thermostat is turned up inside your RV.

You should hear the fan turn on followed by the click of the solenoid. Next you will either hear the rapid ticking or no ticking at all. If you DO smell LP gas at this stage of the process but your RV furnace doesn’t ignite, the problem may well be the ignitor.

Instructions for how to test the ignitor can be found in our post, “My RV Furnace Fan Runs But There’s No Heat”.

A Suburban RV furnace ignitor looks like this:

Suburban 230956 Electrode Assembly
  • package height : 6.35 cm
  • package length : 2.54 cm

Faulty Control Board

And finally, if your RV furnace runs but there’s no heat, there could be an issue with the control board. This is essentially the brain of the RV furnace. Power needs to get TO the control board and also travel THROUGH the control board to the other components of the furnace.

Here again, if your RV furnace runs but there’s no heat and you suspect a faulty control board, visit our post for instructions on how to test the board.

An RV furnace control board:

Your RV Furnace Ignites and Produces Heat But Shuts Off Prematurely

If you turn up your thermostat, your RV’s furnace starts properly and is producing heat, but then shuts off on its own prior to reaching the temperature you’ve set, there are a couple of issues to troubleshoot.

High-Level Switch

The high-level switch (sometimes referred to as a high-limit switch) is the second of two safety switches in your RV’s propane furnace.

It’s the job of the high-level/high-limit switch to shut down the furnace if the temperature in the combustion chamber reaches a certain temperature. This excess heat can be caused by a leak in one of the combustion chamber tubes or by the improper exhausting of the hot air (which could be due to low voltage causing the exhaust fan to run too slowly or by some other failure in the exhaust system).

To address this, make sure that the exhaust is not blocked (by dust, dirt, debris, insect nests, etc.), and that there is proper airflow (check for anything that could be blocking/slowing the air intake for the furnace inside your RV).

You can also check the tubes in the combustion chamber for damage such as holes or cracks.

Should you find no issues after doing all of this, then your high-level switch may be bad. You can test your high-level switch with a multimeter.

This is a high-level (or high-limit) switch:

NOTE: Bear in mind that if you intend to order parts to repair your RV furnace, it’s imperative that you first confirm that the part is the correct part for your make/model.

Flame Sensor

The flame sensor is a critical safety component on your RV propane furnace. When the propane gas is ignited, the heat causes the flame sensor to produce a current of electricity.

However, if the flame in the combustion chamber of your RV’s propane furnace goes out, it will shut down the furnace completely. This occurs so that gas doesn’t continue flowing if it isn’t being combusted.

So, if your furnace ignites and begins to produce heat but then shuts off, the issue could be the flame sensor. The flame sensor is generally part of the ignitor assembly.

What Else Could Cause an RV Furnace to Not Work?

There are a couple of additional easy things to check if your RV furnace isn’t working properly.

Outside Exhaust Vent Blocked or Dirty

It’s important for the furnace’s exhaust port to be free of debris in order for the furnace to ignite and operate normally. Sometimes mud daubers, spiders, or other insects make their way inside from the exterior exhaust port and build nests that create a host of furnace issues.

Removing the exhaust housing and checking for nests and other debris and cleaning the area completely may help.

To prevent this from happening in the first place, installing screens can be extremely helpful.

This is the type that fits the furnace exhaust ports of our RV and may fit yours as well:

Sale
JCJ M-300 Mud Dauber Screen for RV Furnace Outside Fitting
  • RV furnace and fan unit outside fittings
  • Fits DuoTherm and Suburban

You can also purchase a kit like this one with a variety of screens for this and other exhaust ports on your RV:

Sale
RV Furnace Vent Screen for RV Water Heater Vent Cover, RV Bugs Screen,Flying Insect Screen,Stainless Steel Mesh with Installation Tool
  • 【Package Include】: 1x RV Water Heater Screen( 8.5''x 6''x1.3''), 1x RV Water Heater Screen (4.5" x 4.5" x 1.3") , 2 x RV Furance Screen( 2.8" x...
  • 【RV Insect Screen 8.5" x 6" x 1.3"】 : Compatible with Atwood 6 & 10 Gallon and Suburban 6 Gallon water heater vents. Easy to install: It comes...

Air Return Grill Blocked or Dirty

RV furnaces often experience long periods of no use and some are used only occasionally, if ever.

Always inspect your RV’s airreturn grill (and behind it) for dust, pet hair, dirt, and obstructions prior to using the furnace. Be sure nothing is blocking the fresh air return while you’re using the furnace. Keep items away from the return grill while the furnace is in use.

Incomplete Combustion

If your RV’s furnace isn’t working properly, carefully check the exhaust vent for soot. The presence of soot indicates incomplete combustion.

Is your RV furnace not working? Maybe the furnace vents on the exterior are blocked?

When the exhaust vents aren’t hot, use a finger to check for soot at the exhaust ports. Soot build-up is a sign of incomplete combustion.

Make sure to check the exhaust vent only when the vent isn’t hot. Using a finger, check for black soot in and around the exhaust vent.

Should you find black soot in this area, don’t operate the furnace because incomplete combustion can expose you to dangerous carbon monoxide gas. Have your RV furnace inspected by a qualified technician ASAP.

Have You Experienced Issues With Your RV Furnace Not Working?

As always, we’d love to hear from you about any issues you may have experienced with your RV’s furnace and how you resolved them.

And it bears repeating that while it’s good to be able to narrow down what the issue could be using basic troubleshooting methods, RV furnaces can pose significant dangers due to the fact that they use both propane and electricity.

If you have any doubt about your ability to properly troubleshoot and/or repair your RV’s propane furnace, be sure to call a professional to avoid these dangers.

Geek Out with Us Every Week

Join our newsletter to learn about all things RV-related. Every week we offer free tips, tricks, product reviews, and more to our online community of RVers. So, whether this is your first time on the road or you’re a seasoned expert, we’d love for you to geek out with us!

We'd Love It If You Shared This!

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Terry

Tuesday 20th of September 2022

Have a Atwood 8532. Heater does not come on. Hook two blue wires together fan can on but no heat. Any ideas tks

TheRVgeeks

Wednesday 21st of September 2022

Oh boy, Terry. Sorry to hear about that! When you set your thermostat so that the heat should come on, do you hear any noises from the furnace at all? Normally, you'll hear it click... then the fan should start blowing (cold air unfortunately) so that the sail switch triggers (which lets the furnace know the fan is blowing properly), and then you should hear the clicking of the ignitor and then the "WHOOSH" of the burner igniting.

If you're NOT hearing that sequence, you likely have a problem with power (check for inline fuses in the wiring leading to the furnace... there are often several located there and once could be blown) or the circuit board.

scott

Thursday 25th of August 2022

our furnace never worked right when new. it would soot up, make dirty burners, start heat shutoff,etc. we found 8 inches water column and set it at 10.5 and it got worse. last time after a dirty burner . we decided to take it all apart.bought all new parts gas valve igniter, burner, orfis. the whole time it had a orfis for a 35000 btu furnace which is was the largest one available,ours was suppose to be the smallest one the 1.45.after putting it together it runs perfect now. somehow it had the wrong orfice installed and that caused all the problems.

TheRVgeeks

Thursday 25th of August 2022

Oh wow, Scott. Now THAT'S a story! Amazing that you were able to get it resolved! Hope it's keeping you toasty warm (when needed)!

Bill Vosseller

Friday 5th of August 2022

I have a suburban sf25. There is a short in the furnace. The 15 amp fuse blows in the panel Once power and ground are disconnected the fuse is fine and proper voltage is there. Any idea what could be shorting in the furnace. I have it removed and intend to try to find the short before a new purchase.

Brian A Edgerton

Wednesday 4th of May 2022

Hello. I have a 1994 Dutchman with a hydro flame furnace. I don't think my wall thermostat has power. Could you please tell me how to check this? I've checked the fuses. All are ok. Thank you

TheRVgeeks

Wednesday 4th of May 2022

Hey Brian. Sorry to hear you're having trouble. Don't have a specific, end-all-be-all answer for you on this, but can offer a couple of thoughts that may help you track down the problem.

First thought is that RV manufacturers (and their component suppliers) seem to think that fuses are so nice... that they need to be distributed liberally around the RV. So, oftentimes, there can be inline fuses hidden away in frustrating to reach locations. And, in case there's any doubt, we're speaking from experience here. Our own furnace ceased working for us, out of the blue, this past winter. After testing everything, everwhere, and confirming that things looked OK, we remembered that we'd seen an inline fuse in the wiring leading to the furnace itself. "Conveniently" () located behind a panel beneath our refrigerator. Sure enough, a black plastic fuse holder wired inline with the power supply line to the furnace had blown. Why they put it there, instead of in the fuse block with all the other fuses, I'll never know. But, moral of the story, be sure to check right by the furnace to see if there are any fuses there that could be the culprit.

Second thought... if your thermostat is a combined unit that controls your furnace AND air conditioner, then most likely the power comes from a circuit board located inside the cover of the A/C unit itself. Again (of course!), there are fuses on that circuit board that could be the culprit. But, before you start dismantling the rooftop A/C, you can test by just trying to turn the A/C on. If the thermostat works for the A/C, but not the furnace, then it's likely an issue with one of the hidden fuses. Or, at least, is more likely to be an issue with the furnace alone.

Hope this helps! Let us know how you make out... or fire away with other questions. If we can't answer, maybe someone else here will chime in!

Tim Howlett

Friday 11th of March 2022

Thanks guys. Another great, informative article covering- as far as I can tell- the full range of furnace issues from start to finish.

I recently had an “interesting” (aka perplexing) issue where the gas valve for our Atwood furnace was “partially” failing. In our case, the furnace itself was still working fine, but our concern was that we kept getting a (very slight) whiff of propane- the LP gas itself, not exhaust- whenever the furnace was NOT running. An LP gas detector helped me determine that the leak was actually coming out of/through the exhaust port and not from the lines or fittings leading to the valve. So basically what was happening was the valve was closing enough to stop combustion at shutoff, but not seating/closing entirely and therefore leaking gas into the combustion chamber and out through the exhaust port. Replacing the valve fixed the problem. Although I diagnosed the issue down to the valve, I left the replacement to a professional technician as: a) I don’t personally feel comfortable tinkering with LP systems and b) After watching a YouTube video demonstrating the replacement I saw way too many possibilities for seized parts that I didn’t want to tackle out in the desert without my workbench, a solid vice and a full complement of tools. Lol.

Footnote: There was clear evidence of insect (what looked like Stinkbug carcasses) infestation at the valve. I suspect that was the “debris” that was keeping the valve from seating properly at closure, but I can’t look inside the old valve as I don’t have the proper tool to remove the tamper-resistant screws on the valve housing. I have insect screens on all my exterior ports now, but the previous owners didn’t, so I suspect the insects gained access before we moved in!

Unfortunately, my particular furnace problem predated this article, but your methodology definitely would have put me on the right track!

John

Friday 11th of March 2022

Wow! Who would've thunk it! Good catch!

TheRVgeeks

Friday 11th of March 2022

Great sleuthing, Tim! And since discretion is the better part of valor, knowing what you AREN'T comfortable with tackling is just as (if not more) important than knowing what you ARE!

This site uses Akismet to reduce spam. Learn how your comment data is processed.

PLEASE NOTE: We're handy RVers, not professional technicians. We're happy with the techniques and products we use, but be sure to confirm that all methods and materials you use are compatible with your equipment and abilities. Regardless of what we recommend, consult a professional if you're unsure about working on your RV. Any task you perform or product you purchase based on any information we provide is strictly at your own risk.

We participate in the Amazon affiliate program, which provides a means for us to earn a small commission by linking to products there. But our opinions are our own and we only link to products we can recommend to friends with complete confidence. And using our links won't cost you an extra penny!