Troubleshooting An RV Furnace With A Dirty Sail Switch

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Certified Mobile RV Technician Darren Koepp troubleshoots an RV furnace that's not heating due to a dirty sail switch.
If you are in need of RV Repairs in the Olympic Peninsula area of Washington state, submit a service request on our website at myrvworks.com today!

[@carolineua2872]

Darren, I can’t thank you enough for making this video! Had this exact problem and was able to fix my furnace by myself while camping. No more cold nights in the camper. You saved the day! Thank you for being so concise, too!

[@Ponykeg53]

Your great. I love your direct no time wasted descriptions and directions and clear common sense approach to find the problem. You save me so much time. I can't thank you enough.

[@annblack3700]

I have wh6Gea Dominic gas and electric water heater not working on gas or electric . If the switch lights up on control can I assume that it is getting power that the board not getting to heating element in tank. It will not heat water

[@lakesideterri7807]

Thanks so much for making this video! The sun had just set and after feeling a bit of a chill realized the furnace quit. We were able to fix it ourselves thanks to your video! There was just a small bit of fuzz interfering with the sail switch but it was enough to make a difference. Now I'm feeling more confident as well as warm while the temperature continues to drop. Thanks again!

[@TC-pr9nk]

Wanted to add to the multiple thank you comments for providing a clear and precise video to fix our RV heater. You saved the weekend!

[@Strapps31]

You saved us again! Great videos. It takes a massive amount of knowledge to be able to explain complex problems in simple terms.

[@MyRVWorks]

Glad to help

[@folsoml]

Thank you! Thank you! Thank you! The tiniest piece of fuzz was preventing the sail switch from functioning. You saved me a bundle!

[@freetoroam7769]

Thank you for the tutorial. My two year old camper furnace (Atwood) quit working so I found your video, and sure enough the sail switch was dusty. Not sure whey it was so sensitive to light dust, but I blew the dust off and it works great now!

[@604axeman]

I had the same issue. Took the sail switch out, and sure enough, it was caked with lint and dog fur!! Reassembled everything and it works like new!! Thanks for the info!

[@RBG-tr9ce]

It's good to hear from a professional. What I'v found at large RV centers near me is that the "technician" doesn't know anymore than I do. They just want to start replacing parts or the whole unit.

[@eTek891]

Came back at 11pm on a cold night and heater wasn't working. This video saved the..night! Haha thank you for making such a quick and straight forward video!! Also I will add that the sensor had the smallest amount of dust on the switch, which I guess was enought to prevent it from being read. It wasn't nearly as dirty as what was in the video.

[@johnoneil227]

My sail switch wasn't dirty, but I just moved it on and off a few times and that did the trick for the furnace to ignite. Thank you very much for the video!!!

[@kathrynb4683]

Oh thank you so much. This was my problem. Who knew?! Love the way you explain the workings so even if we go to someone like you we know what we're talking about.

[@RobertSmith-xz6kp]

I found your video after a very cold night and morning. You hit my problem right on the head! Next dog will be hairless! Thanks for the great video!

[@patriotprospector8724]

Thanks brother just fixed mine. It was a dirty sail switch. Furnace is running Great now!

[@drgummibear4396]

Spot on Sir. I've had the exact same problem with my furnace. Your fix is correct and so easy that anyone can take care of this problem. Only problem is that something like this always becomes a problem at 3am on a cold night. Right when you need it most. If that happens, sometimes you can get lucky with a well placed thump on the furnace sail switch area (with the furnace cover still installed), while it is purging and you can get it to light and maybe at least get you through the night, so that you can do a proper inspection and cleaning in the daylight hours. This trick worked for me. It's worth a try at 3am. Cheers!

[@josetorres4650]

Thank you for that video my propane heater went out in my rv too this helped and now i have a heater.

[@handtool5408]

Thank you. Your information was exactly what I needed to fix our furnace this morning. 😊

[@NuncaaRetroceda]

Thank you very much, my heater was doing exactly this. I figured it sail switch but had to idea where it was. Fixed in under 5 mins! Warm trailer again :)

[@MarkJonesRanger]

Thanks as well. After watching this video I had my furnace fixed in about 10 minutes. Thanks!

[@racheldoyle7710]

Thank you! So happy I found your channel. Our snail switch had lint on it, cleaned it and it’s working perfectly now.

[@MyRVWorks]

Glad we could help!

[@Tsch6373]

Thank you so much for this video! New subscriber for sure. I appreciate that you get right to the point, I suspected the sail switch since there are no filters in this heating system.

[@moeaskari9679]

Nice, short and thorough!

[@RetiredAtenPilot]

DAm nice job, Clear and to the point !!!

[@toddpomeroy1757]

Boom!!! Fixed. Tying flies in my camper had my sail switch covered in hair and feather particles!!! Thank you!!!

[@MyRVWorks]

Glad it helped!

[@LivingCoast2Coast]

Thanks for the tip. We never know when it may be needed.

[@MyRVWorks]

Glad our videos were able to help you! If you would like to support us please consider becoming an "RV Community Supporter" on our Patreon site: www.patreon.com/myrvworks

[@joeydow2606]

Thanks a lot of that suntec video it was new to me and made my work a lot easier much appreciated

[@FigureItOut_Together]

You are a life saver!!!! Thank you 🙏🏼

[@FreedomIsntFree2023]

Your video prove to be very helpful time and time again....THANK YOU!!

[@tylerelmore9674]

Just wanted to say thank you for this video!!! Fixed the problem in no time. :)

[@TandZAptLife]

This is a great video! We are going to check the sail switch in the morning and I will post here if that solves our problem

[@MyRVWorks]

Thanks for the comment. I have lots of other furnace video's so if this does not fix your issue perhaps I cover it in another video. If not than shot me a message here on on the contact us section of my website: myrvworks.com/contact/ Cheers, Darren

[@backtoobasics]

sweet baby mary, your a genus, thank you for another great video.i love my upgraded unit but the tech is a lil much, shaivn the dog i guess!!stay safe and take care

[@terryjackson6708]

I just wanted to say Thank you Thank you Thank you for your videos. I was able to fix my Furnace last night :) (dirt dobbers ) .

[@sockowe1209]

Thanks, dude. Totally helped me out!!!

[@dirtylu79]

Will try this tmmrw... fingers crossed

[@jimoakley3436]

Got me going on a cool Florida nite thanks !

[@pzwiez]

Thank you, I had a small amount of dust that built up under the switch causing it not to work properly. Cleaned and now we have heat... Too bad it starting to warm up outside. Again thank you.

[@MyRVWorks]

Hi Paul, We are so glad to hear that our videos were able to help you! If you would like to support us please consider becoming an "RV Community Supporter" on our Patreon site: www.patreon.com/myrvworks Happy Camping, My RV Works Media Team

[@sparky5860]

Thank you so much

[@JamesFrady]

This is great thx!

[@philhanly1440]

So Awesome!

[@3Repete]

Hi, I have a 2004 camper with a barely used Atwood 8531-IV heater. Which apparently is the grandparent of some more recent Dometic models. I watched your video because I was getting blower but no ignition. Looked it all over, and I could not see the sail switch any where. Any way I noticed the diagnostic list on the blower housing so I ran it to the fail point, it gave a single blinking light on the control board. In this heater it indicates "Air Flow Limit Fault" which sure sounds like the switch wasn't giving the controller the OK to make fire. I looked and looked for that sail switch. I eventually gave in and pulled the entire heater out of the trailer. Lo and behold there was a removable cover on the blower housing that I feared opening while it was installed. Inside the cover was the sail switch, dead as a doornail. AAAARGH! Well, now I will be able to do a nice job of cleaning, so my father in law with bad breathing will be OK in there! Even though you didn't address my issue exactly, you still gave me some insight into how these thing are set up. Thanks for your videos. They are a great help.

[@andriablack5280]

Where did you find the air flow limit fault I can't find mine anywhere and I'm getting the same 1 flash every 3 seconds.

[@kennygallagher3349]

Nice ! thanks.

[@Rynos9Lives]

Finally a fix that explains all aspects of the system. Thanks. Now it's just a quest to get to the sail switch. Is there a way to test the switch..? Ohms..? Etc

[@MrVanhovey]

Looking for continuity between sail switch and high limit switch, on the same circuit.

[@tray8411]

I have a dometic DF series..brand new 5th wheel coachman.. Blower still runs(after shut off) but makes a pounding noise.. Red light is flashing on mother board... Heater works tho...

[@johnturner4128]

Thanks for the great videos. I just ran some diagnostics and noticed both proofs allow for a complete circuit. My question, I see the battery delivers 8 amps to the board, but the signaling across the sail and HL thermostat is only .72 amps. The proof circuit has 0.14 amps until the click occurs to create flame. Then the sail and HL Stat see .72 amps. Is that expected behavior?

[@georgelutz2787]

Great videos, Darren. But I couldn’t find a discussion about the furnace exhaust. My question is, it seems I have an awfully lot of hot air coming out the exhaust, maybe more than going in my RV. Is it possible to have too much exhaust? Is there a baffle in the unit that may be leaking from the distribution to the exhaust side? Or am I just over-thinking the whole thing.

[@Project_Low_Expectations]

You want as much exhaust as possible. Your flame doesn’t heat the inside air directly, it heats up a heat exchanger which transfers heat to the inside air. A lot of heat goes out the exhaust, but it’s better than carbon monoxide poisoning if you were to try and restrict or redirect the exhaust

[@paultaylor6167]

I have the Attwood 8531 furnace. I want to check my sail switch. I believe I can access it from outside. What parts have to be removed to expose the switch as in this video? Thanks

[@DavidFoxgcm]

Do you have to remove the furnace of your need to change the high limit switch?

[@gregorycarson3889]

Where exactly is sail switch located on an Avalanche 333 mk and how do I get to it.

[@byronargueta3331]

Would you happen to know why my furnace sometimes does not turn on? I watched all your furnace videos but non of them show the same symptom as mine. When my thermostat clicks inside the rv I usually hear the furnace kick on after that but now i can only hear a single click from the furnace . This is the funny part, if I give it a light tap on the side of the furnace it will then turn on. Any idea what cause it to turn on after a light tap on the side?

[@rs3678]

Replaced the sail switch and the limit switch and bingo!!!! fixed. It seems that a restricted register did it when a blanket fell over the one at the base of our bed on the 26XD Redhawk. Damaged the high limit switch.

[@MyRVWorks]

Glad our videos were able to help you! If you would like to support us please consider becoming an "RV Community Supporter" on our Patreon site: www.patreon.com/myrvworks

[@jeffreyengle2762]

The problem I’m having is that so much dirt ends up in the fan and I am wondering is there any way to put a furnace filter on this guy? Where does the primary air intake come from is it right next to the computer board on the left-hand side? Could I theoretically put a furnace filterOn the inside of my coach so that clean air goes through that portion?

[@johnturner4128]

I have been looking at these videos ... do you have a go-fund-me page I can repay back for the assistance provided? Keep up the great work. John

[@triciamyrvworks8263]

Hi John, thank you for the feedback. We do have a Patreon page: www.patreon.com/myrvworks.

[@jaimelopez3991]

Hi, thank you for the video! My furnace is showing 1 light every three seconds which as you said, the sail switch might not be working properly, but the problem is that there is no indication at all of fan blowing air, nothing happens... just the red light flashing every three seconds. Your advise please? Thanks

[@dennisrich2348]

Great videos. Well done sir. Problem I have does not seem to be covered in any video. Furnace starts the motor, then after a few seconds purging the gas lights ( can hear it when it lights), then the gas shuts off and the blower purges and relight. This happens 3 times and shuts the motor off till it is reset. I have checked the exhaust and there does not seem to be any obstruction. It is possible that dirt dubbers are in past where I can see. Or is there a sensor that tells when there is enough air flow to work that is bad somewhere. I am just about to pull the heater which I really don't want to do if at all possible and that may still not allow me to find the problem. HELP

[@andriablack5280]

What did you figure out please? Mine is doing EXACTLY what you described

[@DavidFoxgcm]

Great video Darren I have an Atwood model 2540 sail switch is good but the high limit is done... do I have to remove the furnace to get at the high limit switch? It is a Glendale titanium trailer. Thanks, David

[@andriablack5280]

Where did you find your high limit switch that is my problem now and I'm lost as to which or where it is.

[@DavidFoxgcm]

@@andriablack5280 you would have to look at the schematics of you have them.. However the high limit switch is generally located far and away from the location of the blower motor and all other cluster of components. So for mine, it is locate at the back of the unit on the topside

[@joefacetti]

I have a 2019 Northern Spirit and the access to the sail switch is pretty damn near impossible with how the furnace is installed. Do you have any alternative methods to accessing the sail switch other than having to remove the furnace all together?

[@emilyc2175]

Hi im searching for a solution im going to check my sail switch and now im curious about what tripped thermostat means. I went to bed my heater worked i woke up it had not come back on and now its been 3 weeks no heat using a space heater not super helpful. How would i know if the thermostat was tripped

[@user-ek9vz2un6n]

I have a 93 airstream with a Hydro flame in it, getting a small gas smell after it shuts off any ideas regulator solenoids?

[@craighoyt125]

Hi Guys! Thanks for this... I am having an issue and hope you can help me. I replaced the Sail Switch (it was clean) and that fixed the issue immediately.. and it worked for 2 days.. then went back to only blowing cold air.. and shutting off. I had another sail switch so I switched it out again.. and the furnace worked fine for 1 day... Is something else causing my sail switch to prematurely go bad? Is it the board or the limit switch? thanks!

[@MyRVWorks]

It may not be the actual sail switch that is faulting. You need to make sure that the exhaust port is properly inserted into the furnace, another thing to check is your duct work on the back. The ducts need to be as short as possible with as few as turns as possible. You also need a minimum of four properly sized ducts that all are able to return air back to the furnace (delivering heat to a closed off area like an underbelly does not count for one of the 4 ducts). If there's turbulence in the air leaving the furnace it could prevent a nice even airflow through the furnace itself and that can cause the sail switch to maybe flutter a little bit. So look to any restrictions in your duct work that might be causing improper air flow through the furnace and see if that doesn't help you. Wishing you the best of luck and try to stay warm.

[@javieracosta5528]

Nothing happens when I call for heat from my thermostat. It was working in the morning, then it just quit. My fan won’t even kick on. I can not access my furnace from the outside and would have to crawl into my pass thru storage to get to it. It is an Atwood AFMD25111. I am plugged into shore power and my A/C and roof fan work... but the furnace blower won’t even kick on. Any ideas?

[@DarrenKoepp360]

Hi Javier, if your furnace was working and now it is not my first thought is to check the fuse panel - you have probably already done that if you are here. If all the fuses are good, and the furnace is doing absolutely nothing than it could be one of two issues. First issue could be the furnace is not getting 12 VDC which could be a broken connection somewhere. The only way to test that is to gain access to the wires feeding the furnace. Here is a video I made where I troubleshoot that issue: kzbin.info/www/bejne/onu7hXWantesobM The second issue, is that the control board did not see the sail switch cycle. When the blower is running, the sail switch is ‘closed’ allowing the 12 VDC to pass through the switch. When the blower is not running, the sail switch is ‘open’. When the furnace turns off and the blower stops, the control board is expecting to see the sail switch open. If it did not detect that state than the furnace will not start again! Which sounds a lot like what you are experiencing. This is indicated on the control board via the blinking status light (but if you can get to the furnace that light is doing you no good eh’.) Either way you may need to access the front of the furnace to properly diagnose this issue. I hate when the mfg.’s do not provide access on the outside of the coach to work on the front of the furnace where all the action is! One thing you can try is to pull the fuse feeding the furnace and let the furnace go dead in the water, then reconnect the fuse. Cycling power in that way may cause the control board to forget the state of the sail switch. But if the sail switch is stuck closed than it simply will not work no mater how many times you cycle power and you will have to access the front of the furnace to diagnose that issue. I hope this helps you out! Let me know what you find out. Cheers, Darren

[@silaslongshot941]

You're hot stuff when it comes to fixing furnaces....

[@dawa8746]

Sail switch is clean, but when reset the fan/blower does not come on at all. I came to this from having to cycle the thermostat multiple times where eventually the blower would turn on immediately at the 5 second mark after cycling from AC to furnace. Any ideas?

[@samcasalenda5109]

I cleaned mine still nothing . Prime time avenger… are they universal? If not what item and serial do I go off?

[@tlc2387]

I can't find my ignitor. There is no clear place that it shows on my model SF-35

[@ThunderChicken1]

I bought a new 281 Alliance and I turned on the furnace and it came on. Changed the thermostat to get it to go off. It did, and now won't do anything.

[@deniceloes1552]

Does any aywood sail switch work

[@frankmitzen1162]

Why does my propane tank selector switch freeze up and restricts the flow of propane to my furnace, causing the furnace to blow warm air and run for a long time trying to maintain the temperature setting on my thermostat. What can I do to prevent this.

[@DarrenKoepp360]

Hi Frank, If your LP auto-changeover regulator is ‘freezing up’ than that device certainly needs to be replaced. They have a service life of 10 years. I uploaded a video where I discuss all about the LP pressure in the RV and how to adjust it here: kzbin.info/www/bejne/iXWUopZ-lM2Bj7s Regarding your furnace - if the LP input pressure is below 11” W.C. (discussed in the previously mentioned video) than the furnace will not ignite and/or it will extinguish itself. There needs to be a very specific amount of LP gas in the burner, mixed with air, for there to be, and maintain, ignition. If your RV interior is not warming up, but the exhaust of the furnace is HOT (indicating the furnace is producing heat) than look for a duct that may have fallen off the distribution box on the furnace - it is more common than you might imagine. I have also had to replace entire heater duct sections in RV’s where rodents have eaten through them to gain access. If your furnace is constantly running it would indicate there is no blockage in your ducts as that would trip the high limit thermostat in the distribution box. If all that checks out okay, then we need to do some math to determine the BTU requirement for the interior of your coach and ensure the furnace is sized correctly for your rig. It is rare but I have come across RV's where the furnace was sized incorrectly from the factory! You can find the math equation to determine this in my blog post titled “Darren’s Seminar Outline For Winter RV Living in Comfort” here: myrvworks.com/darrens-seminar-outline-for-winter-rv-living-in-comfort/ Let us know what you find! Cheers, Darren Koepp

[@LorettaPowell]

My sail switch is not easy to get to so instead of pulling out the whole furnace and taking it apart, I just gave it a good whack, now I have heat again. The sail switch was just stuck.

[@bartles55]

Do you need to turn off anything before taking apart the sales switch to clean it?

[@MyRVWorks]

Just make sure there's no call for heat and the furnace is not running. Manufacturers mount sail switches in several different locations. So your mileage may vary. Sometimes you have to take the whole blower cover off, sometimes they're right there on the front of the blower cover, and sometimes they're mounted to the side of the blower cover. But as long as a furnace isn't running you should have no problems removing the sail switch.

[@m3maintenance738]

can a sail switch in a atwood 7916 work and then not work?

[@janetjohnson1202]

Have a. Atwood Hydro Flame 8500-IV series gas furnace that ignites but doesn't stay light. Do you know what could cause this issue?

[@andriablack5280]

Did you figure out your issue? I'm having the same now

[@kristinacook9037]

Mines doing this pre start and starts the propane but then stops, I'm having to reset it over and over and it works for a little bit then stops. Other than the sail switch what could it be?

[@blueeyes3]

So my furnace kicks on but the fan doesn't come on. Could I still have a SAIL switch problem?

[@ismaeltorresrodriguez4677]

my problem is that it works well for 20 seconds it goes off it turns on again like 20 seconds it turns on again it repeats like 5 times and stays off or starts working fine.

[@geoffgallagher7012]

My furnace runs to temperature then shuts off and won't restart just cools trailer off. Have to turn thermostat off and on to re start ?

[@stevepatlan7871]

I have a Dometic DFMD30111 furnace, It starts heating for a few seconds then shuts off and continues to repeat the process. I have replaced the control board but that wasn't it, checked the gap of the electrode as well as check to see if it has an arc which is good. I am at a loss.

[@MyRVWorks]

When you're testing it are you ensuring that the exhaust port is inserted? If the exhaust port is not inserted then it will do what you're explaining here.

[@stevepatlan7871]

That was it, thank you for have the most informative videos

[@christopherjames8317]

I disassembled my Dometic furnace and found there was a bit of lent around the sail switch. Removed it, reassembled, but I still don’t hear an attempted ignition. Any ideas? I’ve been researching this problem off and on since last winter, to no avail.

[@MyRVWorks]

You can diagnosis the circuit with a multimeter. In our most recent video on furnace inspection, Darren talked a bit about following the electric trail and where to test with your meter probes. Hope that helps: kzbin.info/www/bejne/eKG0eZZslLOqhrc

[@DescribeSomeWords]

My furnace is kicking on but only staying on for a few minutes and then doesn’t come back on until I’ve turned it off and waited for awhile. What could be the cause for that?

[@moeouellette1968]

If my furnace works fine on 120 power,but wont ignite on 12 volt,could it be the sail switch??

[@MyRVWorks]

Need a bit more info on your furnace. Is your furnace in a park model and therefore has a 120 VAC motor? That being the case there is a transformer to convert to 24 VAC for the thermostat but all of the controls are 120 VAC and there is no 12 VDC involved. On RV's the furnace motors and controls are all 12 VDC. If you can provide the complete model number it will really be helpful. I do have many more furnace video's on my playlist here: kzbin.info/aero/PLk44vSl27TRCaZIQbm-0utYK7sVOKwXVY See if any of these will help.

[@aussiesandtrails]

Mine was working fine for the past 2 30 degree cold nights tonight it stopped working. Blower doesn't come on. Could it be the sail switch. Both propane tanks are at 80% full. I only have one propane tank open. Connected to shore power and 12v battery is full as well.

[@MyRVWorks]

It's possible it's the sail switch, but the only condition where that would be true is if the sail switch was stuck closed. If you can get to the front of the furnace and see the control board it may be blinking a light which would indicate the fault. Having said that, if the sail switch is fine then you may be looking at a blown fuse somewhere. You need to verify the furnace is getting power 12 volts dc.

[@aussiesandtrails]

@@MyRVWorks I checked my converter box and done see a dedicated fuse for the furnace inside is the fuse on the board itself?

[@kathrynb4683]

I have an 8535 model and the sail switch is not in that location. Do you know anywhere else it could be?

[@andriablack5280]

Where did you end up finding yours? I have same model and mine isn't where it is in this video either.

[@user-up3ck5dj7v]

My ac stopped working we took case off found a loose yellow wire I don't know where it goes

[@jjlarson74]

What if your sail switch is NOT where you say it is?

[@melinda2625]

What if there is no sail switch showing?

[@corymcthrash]

Yay! Thought my sail switch was bad, was just doggie hair

[@brianbiggs3484]

👍👍🇨🇦✌️🇨🇦✌️🇨🇦👍 Thanks Darren !!!

[@jeffeisenbrei7128]

My furnace working on bench test not in rig Elma WA

[@MyRVWorks]

Hey Jeff, Did the sail switch that we talked about fix the issue? Cheers, Darren

[@PeeWeeHenson]

OK. I CLEANED MY SAIL SWITCH. PUT EVERYTHING BACK THE WAY I FOUND IT. STILL NO IGNITION. WHAT COULD BE MY PROBLEM?

[@rmedrano463]

JUST HOW I LIKE MY YOU TUBE VIDEOS? SHORT AND TO THE POINT!

[@lisahawkins1430]

Furnace was working fine. Now it just clicks. Help

[@gdcat777]

That is NOT where my sail switch is, I can't find it.

[@MyRVWorks]

Different manufacturers put them in different places - and even within a manufacturer's model range they'll be located in different places. There is no one spot. You can follow the wires. Mostly they're blue or white wires. They're going to be located in one of your blower wheel covers.

[@hreyes425]

My furnace isn’t working right not sure if it might be the sail switch. The blower turns on then the clicking but won’t ignite. But if I put my hand in front to create pressure it kicks on if I remove my hand it shuts right off. So I put a piece of 2x4 to stay longer left it for a minute and would stay on no issue. I shut it off for 30 minutes to see if it’s working again and same results happened. So I did the 2x4 method again let it run for a bit then shut it off till I heard the burner shut off turned it back on with no issues, no 2x4 method needed.

[@MyRVWorks]

To schedule a service consult with Darren please sign up for the "1:1 Repair Consult" on our Patreon site. www.patreon.com/myrvworks