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Old 11-22-2021, 09:53 PM   #1
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Dometic furnace - fan, no heat

On a 2021 Wanderer 24FSWL - without any cold weather stuff. This happened the past couple of trips. Fire up the furnace, fan fires up, blows strong and no heat. Running in/out (or having a second set of hands turn on the heat inside) no 'click click click' is heard, indicating any attempt to light.

First happened - was up in northern UT. Got back home, it fired right up without an issue. Figured just a glitch or dust/debris in the exhaust. Gave it a quick once-over, pulled the cover, cleared any dust or crap found (nothing to write home to), tried to fire it up in the driveway and it worked as expected.

Thought was all good, put it in storage, brought it back for another northern AZ trip (again not stupid cold out where we went) - verified it turned on and worked in the driveway, nadda up north.

Other propane devices (stove, oven, fridge, water heater) all working as expected. Come back home - everything works just fine.

Throw a new deep cycle battery...again it works just fine at the house. Refilled both tanks, followed 'slow open to 100% thing of propane bottles, let fridge do it's thing to fire up, fired up the oven, all 3 stove burners and water heater to verify good gas flow to everything. Again, furnace fires up and works like a champ in the driveway.

Head up north again this past weekend (was smart, I brought a small electric space heater along as it was going to be mid-low 30's overnight, 50s during the day). Same thing... I don't know if it worked the first night or not to be honest. I heard it kicking on/off and we were sweating overnight with the extra blankets so I'm guessing so (was set to 67 furnace-mode, running on battery overnight). Next day...nadda. Battery juice was down to 50% - fired up the genny and let it re-charge the battery. Furnace never turned on again the whole trip. We ended up using the space heater to warm the camper up before we went to sleep and just bundled up. Wasn't too bad - only dropped down to about 50 in the camper.

Got a slew of things that I think it could be but when I think more about it, the symptoms don't line up. Dometic troubleshooting guide is all but worthless - it says if the fan turns on, bleed the air and/or increase the temp.

Bad Sail switch. If it was a bad sail switch, why would it work at home and not up north. My guess - elevation? Home is about 1100'. This last weekend we were around 6900'.

Bad propane regulator - but again all other propane devices were operational. Don't recall the flame color when we fired up the stovetop - but all other propane appliances were working from the get-go. Tried disconnecting/emptying/reconnecting/reopening the tanks and switching tanks - to no avail.

Next thought - bad propane mix? Maybe the propane mix I have isn't suited for colder weather?

I have a call out to my dealer service where I purchased at. Last time it went in for repairs I didn't have it for almost 5 months...and I don't want that again (another intermittent issue I had that was hard to replicate). With being here in the valley, we don't get frequent low-30 degree temps or 50 degree days.
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Old 11-22-2021, 10:05 PM   #2
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I have no clue on why it is doing what it is doing, but just as a starter I would suggest you or anyone reading this to get a set of screens to put over the inlet and exhaust ports of the furnace. Insects and other critters can and will find their way into the furnace blower and cause grief. I hope someone here has a better answer.
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Old 11-22-2021, 10:24 PM   #3
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Air/Fuel Mixture

At 1100' all normal with in ratio

At 6800'...thin air/furl Rich
Propane has a Narrow flammability range 2% - 9.5%
Propane below 2%...no ignition
Propane above 10%...no ignition

At elevation sail switch could also be hanging up...paddle moving against cover/not fully closing so no sail switch no DC to circuit board for gas valve/spark electrode firing---no ignition
*paddle might need a little tweak so it moves freely
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Old 11-22-2021, 10:29 PM   #4
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Quote:
Originally Posted by 4thgenceli View Post
On a 2021 Wanderer 24FSWL - without any cold weather stuff. This happened the past couple of trips. Fire up the furnace, fan fires up, blows strong and no heat. Running in/out (or having a second set of hands turn on the heat inside) no 'click click click' is heard, indicating any attempt to light.

First happened - was up in northern UT. Got back home, it fired right up without an issue. Figured just a glitch or dust/debris in the exhaust. Gave it a quick once-over, pulled the cover, cleared any dust or crap found (nothing to write home to), tried to fire it up in the driveway and it worked as expected.

Thought was all good, put it in storage, brought it back for another northern AZ trip (again not stupid cold out where we went) - verified it turned on and worked in the driveway, nadda up north.

Other propane devices (stove, oven, fridge, water heater) all working as expected. Come back home - everything works just fine.

Throw a new deep cycle battery...again it works just fine at the house. Refilled both tanks, followed 'slow open to 100% thing of propane bottles, let fridge do it's thing to fire up, fired up the oven, all 3 stove burners and water heater to verify good gas flow to everything. Again, furnace fires up and works like a champ in the driveway.

Head up north again this past weekend (was smart, I brought a small electric space heater along as it was going to be mid-low 30's overnight, 50s during the day). Same thing... I don't know if it worked the first night or not to be honest. I heard it kicking on/off and we were sweating overnight with the extra blankets so I'm guessing so (was set to 67 furnace-mode, running on battery overnight). Next day...nadda. Battery juice was down to 50% - fired up the genny and let it re-charge the battery. Furnace never turned on again the whole trip. We ended up using the space heater to warm the camper up before we went to sleep and just bundled up. Wasn't too bad - only dropped down to about 50 in the camper.

Got a slew of things that I think it could be but when I think more about it, the symptoms don't line up. Dometic troubleshooting guide is all but worthless - it says if the fan turns on, bleed the air and/or increase the temp.

Bad Sail switch. If it was a bad sail switch, why would it work at home and not up north. My guess - elevation? Home is about 1100'. This last weekend we were around 6900'.

Bad propane regulator - but again all other propane devices were operational. Don't recall the flame color when we fired up the stovetop - but all other propane appliances were working from the get-go. Tried disconnecting/emptying/reconnecting/reopening the tanks and switching tanks - to no avail.

Next thought - bad propane mix? Maybe the propane mix I have isn't suited for colder weather?

I have a call out to my dealer service where I purchased at. Last time it went in for repairs I didn't have it for almost 5 months...and I don't want that again (another intermittent issue I had that was hard to replicate). With being here in the valley, we don't get frequent low-30 degree temps or 50 degree days.
What you are describing can only be one of four things. The sail switch, the time delay relay, the high temp switch or the control board.

I would be leaning towards the time delay relay or control board. Normally if a sail switch fails you will hear the click of the igniter but the gas valve does not turn on to light it.

Since you are describing an intermittent problem youíll need to test it when it is not working. Old biscuit is the pro on these things. Do a search with the google tab at the top of the page. He has posted the 12v power test sequence so many times I swear he has it save so he can copy and paste.

That said, in my previous coach, my furnace would work just fine with fully charged batteries and on shore power. I figured sail switch. Took it apart and it had the plastic squirrel cage fan. Two fins were broken on it, so at anything but 13.6 volts it did not blow enough air to trip the sail switch.

The only other thing I can think of that might cause intermittent problems is an obstruction to the air flow. Check the input and exhaust on the flue side, but also check the input and vents inside the coach. Either one not moving enough air can keep the sail switch from working.

As far as a dealer keeping my coach for 5 months, I would find another dealer. If it is still under warranty reach out to the manufacturer as they need to know the treatment their customers are getting.
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Old 11-22-2021, 10:34 PM   #5
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OP has a brand new furnace.
No Time Delay Relay Used...circuit board handles that function

BLW circuit (t-stat closes supplies DC) sends DC to Fan Motor

Sail Switch HAS to close for DC to go back to circuit board for Gas Valve AND spark electrode to be energized
*DC to/thru Sail Switch then to/thru Limit switch>>>circuit board

Testing would need to be done at elevation where the issue occurs
*works fine at lower elevation


Suburban/Atwood/Dometic......all use the same DC circuits
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Old 11-22-2021, 10:50 PM   #6
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Quote:
Originally Posted by amosnandy View Post
What you are describing can only be one of four things. The sail switch, the time delay relay, the high temp switch or the control board.

I would be leaning towards the time delay relay or control board. Normally if a sail switch fails you will hear the click of the igniter but the gas valve does not turn on to light it.

Since you are describing an intermittent problem youíll need to test it when it is not working. Old biscuit is the pro on these things. Do a search with the google tab at the top of the page. He has posted the 12v power test sequence so many times I swear he has it save so he can copy and paste.

That said, in my previous coach, my furnace would work just fine with fully charged batteries and on shore power. I figured sail switch. Took it apart and it had the plastic squirrel cage fan. Two fins were broken on it, so at anything but 13.6 volts it did not blow enough air to trip the sail switch.

The only other thing I can think of that might cause intermittent problems is an obstruction to the air flow. Check the input and exhaust on the flue side, but also check the input and vents inside the coach. Either one not moving enough air can keep the sail switch from working.

As far as a dealer keeping my coach for 5 months, I would find another dealer. If it is still under warranty reach out to the manufacturer as they need to know the treatment their customers are getting.
I'm hard up to think it's anything 12v related - but I have been wrong once before. It acts the same on/off shore power (shore power in this last weekend trip being a 4500w genset). Tried it with nothing running except for the furnace both on battery and genset power - still same behavior. Only thing I didn't do this last trip was run out side and listen to see if it was trying to ignite - cuz uh... 28 degree wind chill factor :P

I thought airflow as well - but it's blowing plenty strong (blew the towels right off the oven door). While a full cleaning/inspection wasn't done yet, a quick cursory inspection camera snaked down the pipes didn't throw any alarms. The hard thing is the testing it- I'd need to haul it somewhere colder to test (or higher elevation/colder) to replicate the scenario of inoperability.

Biscuit - I didn't think about A/F ratio on the heater itself being out of whack. Some of the roads we've traveled you could wash clothes on - maybe that got jarred a bit or something electrical jarred just enough loose. Just really strange - a year ago it was just fine and we roughly in the same area, a bit higher up (~8100') during an elk hunt. Heater worked like a champ that whole week with similar overnight temps. Come to think of it - that was the last time it worked consistently (granted a lot of our trips we don't use the furnace much as they're summer trips somewhere out of the furnace and into 'reasonable' summer temps where the overnight low isn't 95 degrees).

I did approach the dealer - they have a few locations here in the area. When the brake issue first arose, I took it to the one closest (which happened to be up north). After three months it was 'Meh, we can't replicate it'. Hooked up and went to bring it home (bigger/badder truck that could handle it downhill without brakes), took it to the main service center here in the valley and they had it diagnosed and fixed within a month (needed a second trip back due to another unrelated issue, so overall 5 months gone). They very much heard the grief - and extended the 12mth warranty due to the northern service issues.
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Old 11-22-2021, 11:14 PM   #7
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Jarred .....but it worked in driveway and didn't at elevation

No Click/Click/Click at elevation suggest sail switch hanging up
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