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!
- 1) How Does an RV Furnace Work?
- 2) What Are RV Furnace Diagnostic Codes?
- 3) Typical RV Furnace Wiring Diagram
- 4) The Most Common Reasons Why an RV Furnace Is Not Working and How to Troubleshoot Them
- 5) What Else Could Cause an RV Furnace to Not Work?
- 6) Have You Experienced Issues With Your RV Furnace Not Working?
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.
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.
- 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:
- 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:
Atwood/Dometic blower wheel:
- Fits 8500 III & IV series
- Package Dimensions: 13.208 L x 17.78 H x 13.462 W (centimeters)
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:
- When your would run normally, if you hear the igniter begin to fire, then the furnace would light, then immediately go out.Maybe you can consider the...
- This sail switch designed for rv and campers heater furnace fault use.
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:
- Replaces Suburban 161122 Gas Valve
- OEM names and numbers used for reference only.
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:
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:
- FAN50PLUSPINS
- Size: 3.35" x 4.25"
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:
- Product Type :Auto Accessory
- Package Dimensions :9.5" L X8.5" W X1.5" H
You can also purchase a kit like this one with a variety of screens for this and other exhaust ports on your RV:
- 【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 Atw-ood 6 & 10 Gallon and Sub-urban 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.
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.
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Thomas Burriss
Saturday 30th of March 2024
The heater in our camper would not come on unless we turned the heater off, then back on. Figured it was the thermostat, so I replaced it with the same name brand ( Coleman) but upgraded to the digital version 8330-3862. It worked fine for awhile, but now, is doing the same thing. Any ideas. Figured I’d try this before I called a service man.
TheRVgeeks
Saturday 30th of March 2024
Hi Thomas. Hmmm... that one's gonna require putting on a Sherlock Holmes hat and doing some sleuthing. Sounds like it's possible it's a battery voltage issue (does it work better if you're plugged into shore power than when you're not?)... or it could be an airflow/"Sail Switch" issue (the "Sail Switch" is responsible for detecting that the blower is operating at fast-enough speed to ensure that the furnace doesn't overheat and that exhaust gases from the burned propane are properly evacuated out the exhaust pipe). It could also be a propane supply issue... if the tank(s) are low, and the ambient outdoor temps are very low, the vapor pressure in the tank drops, resulting in not enough propane gas to keep the furnace running.
So... as you can see... it could be a LOT of things, and may require doing some more testing and observing. Have someone outside by the exhaust from the furnace to listen for sounds. When it stops running, do you hear the "click-click-clicking" of the ignitor trying to reignite the propane? Does it just shut off. Check battery voltage at that time (preferably with a multimeter: this is the one we use, but this cheaper one will do the job, too.)
Donna
Tuesday 12th of March 2024
We have a 1997 forest river serrea that is permanently parked. Last fall our furnace ran but did not produce heat. We made sure we had propane on but we still couldn't get heat. We removed the furnace and had it bench tested at a camper dealer and they said it tested alright. we reinstalled the furnace. Now the furnace produces heat but it still is not right. When it starts up we hear the fan running and the igniter clicking but I don't hear the whoosh like it used to make. It makes a louder noise and sometimes after it has ignited I can hear the clicking sound continuing and sometimes it makes a noise like the flame going off and starting again while the furnace is running.
TheRVgeeks
Tuesday 12th of March 2024
Hi Donna. Sorry to hear about your trouble! This one is definitely a bit of a head-scratcher, since the furnace bench-tested to spec, but isn't working once installed in the RV. Our bet would be that there's some issue with the propane supply (i.e. flow rate, pressure, or even a pinhole leak in a supply line) or air flow (blocked ductwork, blocked air intake for the burner, or blocked exhaust) that's causing the problem. The pattern on a properly functioning RV furnace should be (1) blower fan comes on for as much as 30 seconds (allowing the electronics to confirm good air flow), (2) clicking of the ignitor, (3) WHOOSH/RUMBLE of the burner igniting, and then (4) AHHHHHHhhhhhhhh as the warm air starts flowing! 😉
It could even be a voltage issue... if your unit is permanently parked, batteries could be aged out or the 120V AC-to-12V DC converter/charger could be going. Fluctuations in voltage, or noise on the 12V DC side of things, could be interfering with the electronic "brains" of the furnace. Or low voltage could be causing the fan speed to slow down... resulting in the sail switch telling the furnace to stop the flow of propane... hence the "re-lighting" clicking you're hearing.
Is you trailer hooked up to a larger propane supply (like a large external tank, connected using an Extend-a-Stay style adapter)? And is the hose connecting that tank to the RV larger than about 10 feet? If so, there's a condition where cold temperatures can cause an oily residue to be formed in large runs of flexible hose... and that oil can clog (and reduce the flow from) the RV's onboard regulator. Since the furnace is likely the appliance requiring the highest flow of propane, it could be "the canary in the coal mine" and alerting you to an issue there. You'd have to remove the regulator to see whether or not an oily substance comes out of it (if it does, you'll need to replace it... and either shorten the length of hose connecting the external tank to the RV... or add a 15PSI regulator on the large external tank, which will drop the pressure in the hose down to a level that won't allow the oil residue to form, but which is still high enough for the RV's onboard regulator to "open" and allow propane to flow... going much lower than 15PSI could cause an issue that wouldn't allow propane to flow).
Have you noticed any other propane appliance misbehaving? Stovetop? RV refrigerator running on propane?
As you can tell... there's a LOT that could be a factor here. If you aren't able to troubleshoot these yourself, you may need to get a mobile tech to come out so they can see the problem first hand. If they're good with propane issues, they may have a manometer to test the pressure and flow of the propane at the furnace connection, which may help identify that as the cause, or eliminate it.
Best of luck (spring is coming!)!
James
Friday 29th of December 2023
2018 Leprechaun with Dometic DFMD30141 30,000 btu furnace. Trying to get ready for winter and furnace not working. No problems in the past but..... Typical 3 flash light saying ignition lockout. Replaced sail switch and same failure. Just replaced Atwood 31501 controller board, installed cover and same problem. Furnace turns on and in a few seconds can hear and smell propane. Furnace lights and feel hot exhaust for a few seconds and then cuts off. This happens 2 more times and then locks out. Tried reset and same failure. No obstructions that I can see. Seems like everyone who replaced board says that solved problem..but not mine...Any suggestions on next steps?
James
Saturday 30th of December 2023
@TheRVgeeks, BTW, I look on parts breakdown for furnace and do not see thermocouple/thermistor. Would that be the same as Hydroflame RV Furnace Igniter Electrode? thanks much again!
James
Saturday 30th of December 2023
@TheRVgeeks, Thanks for suggestions and I'll look into those 2 before going professional. Appreciate your site and comments!!
TheRVgeeks
Friday 29th of December 2023
Oh no, James. We feel your frustration… we hate it when the expected repair doesn’t work! From what you’re describing (furnace fires up, but doesn’t STAY lit) it sounds like it could be an issue with the thermocouple/thermistor that detects the flame. If that’s malfunctioning, the furnace will shut off… since it would be a bad idea to keep allowing propane to flow if it’s not being burned up. Explosion hazard.
Another option could be a bad burner orifice. We had something similar happen on an old Norcold RV refrigerator… there was a crack in the tiny “gem” that’s used to make the orifice opening to allow the propane out. On the fridge, it caused a “popping” noise when it was burning to run a cooling cycle. On the furnace, it could be preventing the burner from staying lit by messing with the propane-to-air ratio.
Other than that? It may be time to get a professional’s eyes on it. It gets expensive continuing to throw parts at a problem. 🤔
Richard K Batewell Jr
Friday 29th of December 2023
Heat works great when hooked to electric, doesn’t do anything when unplugged. Duel deep cells are new and have plenty of power. Propane is full and everything works great. So I started the heat wile plugged, then unplugged and the furnace turned off but the fan continued. Waited for it to shut down and tried to turn heater on wile unplugged and nothing. I want to go boondocks but without heat sound bad to me, it’s cold out there.
TheRVgeeks
Friday 29th of December 2023
Oh no, Richard. SOOOO sorry to hear about this trouble. This is a head-scratcher! Without being there to put hands on, it's a little hard to troubleshoot. But we have some questions/thoughts that may help you isolate the trouble:
Is it possible your RV has something like the CheapHeat 120V heating element that allows you to run your furnace as a big electric heater instead of running propane? If so, perhaps that's causing interference with the furnace's operation on DC? If you can access the area where the furnace is installed (in our Mountain Aire, that was beneath the fridge and was accessible from inside the RV by removing a panel from beneath the fridge), look for every electrical wire running to/from the furnace and follow them as long as you can see/reach. Look for inline fuse holders... and check those fuses. For some reason, every furnace we've ever looked at in an RV had at least one fuse somewhere inline with those wires, instead of being in the central fuse block with all the others. It's possible one of these fuses has blown and that's causing the trouble. Does your RV have an air conditioner (or more)? If so, RV manufacturers typically use the brains in the air conditioner (the front one if you have multiple) as the "master" controller for the HVAC system. As a result, that main A/C unit has some settings (DIP switches, usually) on a circuit board inside the A/C unit itself. Those control what types of heating options are included (i.e. is the A/C a heat pump? Does it have heat strips installed? Is the furnace propane? Or diesel hydronic? Etc.). It's possible something is wrong there (unlikely, unless you recently had someone working on your A/C unit(s). In the same vein as above, the main A/C unit is supposed to communicate that information set by the DIP switches to the thermostat. Sometimes, that info gets garbled so the thermostat doesn't function correctly. Each brand/model has their own reset procedure(s), so you can Google for "XXXXXX RV thermostat reset procedure" to try to find the steps. That may rectify things. Lastly, it's possible that your thermostat has just given up the ghost. If it's a new RV, it's less likely, but if you have a 10+ year old unit... well, could be time.Of course, it's also possible that the wire connecting the thermostat to the A/C unit or furnace has also been damaged (mice, perhaps?)... though that wouldn't really explain why it would work on shore power, but not on battery.
Sorry we don't have more definitive advice to offer, but we hope one of the above at least gets you on the right trail. Please follow up and let us know what you find out... or to ask additional questions (year, make & model of RV as well as brand and model of furnace would help).
Adam
Sunday 5th of November 2023
My 99 pace arrow vision has dual furnaces and they both stopped working and the water heater stopped to they will not turn on at all
TheRVgeeks
Tuesday 7th of November 2023
Oh boy, Adam! Sounds like it's either the battery is bad (do other 12V items like lights or fans work? Are they full bright and/or full speed?) OR you're low/out of propane (does the stovetop light?). Hope it's one of those two!