Dometic furnace sail switch rehash/update

[ri-f]

There has been plenty of discussion on sail switches for the Dometic furnaces that were having trouble with igniting and staying lit. I just bought a spare sail switch w/bracket for mine (I wasn't having a problem, but simply wanted a backup): Mine is Dometic model DFSAD12111 (installed in a 2020 Hawk shell). My furnace has serial number 94486978 (your serial number is used by Dometic to determine the correct sail switch and bracket required for any particular furnace). Dometic told me today that they had problems with some of their sail switches and they upgraded the switch. The original OEM sail switch model number for mine was #33082 (which is what FWC says they keep in stock for replacements. repairs, etc). But Dometic says that those were problematic switches and they recommend not using those, but instead using model #33081, because it was redesigned to work correctly. This may or may not be the correct sail switch for your particular Dometic 12,000 BTU furnace, you can only confirm this with your model number and serial number and a call to Dometic support for any upgrades they may have available for your particular furnace. It could make a difference in your furnace's performance (or lack thereof). Just a heads up for anyone who might be concerned.

Rich

 

[Lee Murian]

Thanks for this information. As the owner of a 2020 Hawk that had furnace issues, I'm going to check my unit but as the same model year, I would suspect same furnace. I've had my camper off for the winter and am planning to install this week. Would be good to know if there is a solution.

 

[JWL]

It begs the question why FWC doesn’t send the defective ones back to Dometic and get the current ones??
I guess because it’s the same reason why they can’t come up with a fix for the bad vent design in the Hawks. Which so far is the only issue I have had with my furnace. But this is good to know for when this happens.

 

[Wallowa]

It begs the question why FWC doesn’t send the defective ones back to Dometic and get the current ones??
I guess because it’s the same reason why they can’t come up with a fix for the bad vent design in the Hawks. Which so far is the only issue I have had with my furnace. But this is good to know for when this happens.

Bad vent design in Hawk? I missed that; what are the details.

 

[ri-f]

Bad vent design in Hawk? I missed that; what are the details.

I believe that reference is to the vent cover, which is offset to the duct behind it, creating a slight bend in the duct and narrowing the opening. This may restrict full air flow and that may prevent the burner from staying lit. This has been reported as a problem. If this happens, the solution is to unscrew the furnace cover, on the inside of the camper, and un-kink the duct (or shorten the duct length so it can't bunch up and restrict the air flow). This hasn't happened to me, but it has happened to others.

 

[JWL]

I believe that reference is to the vent cover, which is offset to the duct behind it, creating a slight bend in the duct and narrowing the opening. This may restrict full air flow and that may prevent the burner from staying lit. This has been reported as a problem. If this happens, the solution is to unscrew the furnace cover, on the inside of the camper, and un-kink the duct (or shorten the duct length so it can't bunch up and restrict the air flow). This hasn't happened to me, but it has happened to others.

Yes that’s it. FWC came out with a vent cover that has the duct opening off center so it is in line more with the furnace opening. After scrunching, shortening etc. the duct on mine to no avail I tried to get this “new and improved “ face plate and was told that it didn’t work either. The new “fix” is to just remove the duct. That works but I feel a lot of the heat stays in the furnace box. Not very efficient…

 

[Wallowa]

Yes that’s it. FWC came out with a vent cover that has the duct opening off center so it is in line more with the furnace opening. After scrunching, shortening etc. the duct on mine to no avail I tried to get this “new and improved “ face plate and was told that it didn’t work either. The new “fix” is to just remove the duct. That works but I feel a lot of the heat stays in the furnace box. Not very efficient…

Thanks for this...can you explain what exactly "didn't work"? Did the flex tubing kink and you could see this through the plastic plate over the outlet inside the camper? What went wrong with the furnace; back pressure that shut the furnace down?? Need to understand to monitor mine.

Also does the model of FWC change the furnace ducting? And side vs front dinette?

Thanks again...

 

[JWL]

Thanks for this...can you explain what exactly "didn't work"? Did the flex tubing kink and you could see this through the plastic plate over the outlet inside the camper? What went wrong with the furnace; back pressure that shut the furnace down?? Need to understand to monitor mine.

Also does the model of FWC change the furnace ducting? And side vs front dinette?

Thanks again...

I’m not sure about other models, I know it is primarily in Hawk Shells so I don’t know why the other Hawk layouts would be any different.
The furnace opening sits on the right side of the cabinet and the faceplate opening is in the center. So in about 3 inches of space the flexible duct has to go from right to center and allow for the bends to make the connection. All of which restrictions airflow enough to not all the furnace to start.
Here are some pics
The one with the vent was after shortening as much as I could and still get my hands in to attach, it still didn’t work.

 

[ri-f]

14E10DA0-AB27-4E38-836A-1FEAE94B2774.jpeg
I’m not sure about other models, I know it is primarily in Hawk Shells so I don’t know why the other Hawk layouts would be any different.
The furnace opening sits on the right side of the cabinet and the faceplate opening is in the center. So in about 3 inches of space the flexible duct has to go from right to center and allow for the bends to make the connection. All of which restrictions airflow enough to not all the furnace to start.
Here are some pics
The one with the vent was after shortening as much as I could and still get my hands in to attach, it still didn’t work.

JWL - Are you certain that the vent offset is the primary problem? Does removing the flexible duct always solve the problem of the furnace not staying lit or is it hit and miss? You've tried swapping out the sail switch kit? The only other thing I can think of that might cause the burner to not stay lit, assuming all the electronics are OK (circuit board, etc,) is the igniter gap being too narrow. The gap is supposed to be 1/8" but some have reported success with a wider gap of say 1/4". And lastly, if you turn the knob on the propane tank valve too quickly when you first try to start up the furnace it could also cause an issue with the igniter not working. Try turning the valve on very slowly. If it really is just the vent, then the only other suggestion might be to possibly make your own vent face plate so that it is positioned properly for full air flow. Maybe attach a fixed, short, sheet metal duct, like a stove pipe so it can't bend and kink up, and run it directing to a new face plate with a rotating vent that you could buy and insert in the face plate directly in front of the new sheet metal duct. Just a thought. Rich

 

[DarinH]

It begs the question why FWC doesn’t send the defective ones back to Dometic and get the current ones??

As recent as late March, they apparently haven't. I picked up my 2021 Grandby in late March and slept in it the first night on shore power, in Montana, and the heater worked like it should. 2 weeks later I'm camping off grid in northern Utah, and the heater would not stay lit for more than a few minutes with fan running on a fully charged battery. When I would have the truck idling, it would stay lit, but I'm not going to idle my truck all night. Good thing I had a warm sleeping bag those 2 nights.

 

[JWL]

JWL - Are you certain that the vent offset is the primary problem? Does removing the flexible duct always solve the problem of the furnace not staying lit or is it hit and miss? You've tried swapping out the sail switch kit? The only other thing I can think of that might cause the burner to not stay lit, assuming all the electronics are OK (circuit board, etc,) is the igniter gap being too narrow. The gap is supposed to be 1/8" but some have reported success with a wider gap of say 1/4". And lastly, if you turn the knob on the propane tank valve too quickly when you first try to start up the furnace it could also cause an issue with the igniter not working. Try turning the valve on very slowly. If it really is just the vent, then the only other suggestion might be to possibly make your own vent face plate so that it is positioned properly for full air flow. Maybe attach a fixed, short, sheet metal duct, like a stove pipe so it can't bend and kink up, and run it directing to a new face plate with a rotating vent that you could buy and insert in the face plate directly in front of the new sheet metal duct. Just a thought. Rich

in my case 100%. It doesn’t even get to tying to light, it starts blowing and shuts off. Apparently this has been going on awhile, our first trip with the camper it wouldn’t start and our friends with a 5 year old Fleet told me to try taking the cover off because when he had problems with his they told him to try that. (He got all the “sail switch” run around 3 times and it ended up being a gap issue)
When I got back I called and Aaron said I was on the right track and they were aware of the problem. Stan sent me this pic of the cover they were working on with the offset opening. After this last trip I emailed Stan asking for one, waited a week, emailed Stan and Aaron asking for one, waited anther week and called Jay and he said “yeah, those didn’t work. Just leave the flexible vent off.”
The problem seems to be altitude. I had it working once in Texas around Christmas but this last trip to NM and Utah the first morning at only 5500 ft it was no go until I yanked the vent off and it worked for the next 5 nights without a problem. And it is still off!
You would think with all the campers they have made through the years and for the $1495 they charged for this furnace they would make sure they actually worked.

 

[ri-f]

in my case 100%.
...The problem seems to be altitude. I had it working once in Texas around Christmas but this last trip to NM and Utah the first morning at only 5500 ft it was no go until I yanked the vent off and it worked for the next 5 nights without a problem. And it is still off!
You would think with all the campers they have made through the years and for the $1495 they charged for this furnace they would make sure they actually worked.

Well, that's a drag. Sorry to hear that. At least you can get it running without the face plate (but it does seem odd that a properly aligned face plate and duct doesn't work). I've heard of a couple others on different forums discussing this and apparently altitude was their problem as well. Their fix was the gap - they increased the ignitor gap from 1/8" to 1/4" and that worked for them. They never had an issue after that. This was in Colorado above 10,000 ft.

 

[steve whiteside]

I believe that reference is to the vent cover, which is offset to the duct behind it, creating a slight bend in the duct and narrowing the opening. This may restrict full air flow and that may prevent the burner from staying lit. This has been reported as a problem. If this happens, the solution is to unscrew the furnace cover, on the inside of the camper, and un-kink the duct (or shorten the duct length so it can't bunch up and restrict the air flow). This hasn't happened to me, but it has happened to others.

I had the same issue on my grandby. Ended up just removing the flexible duct. Withe the duct in I couldn't get the heater to stay lit. Without the duct, it "sprays" the heat around a bit more but at least it works.

 

[Mthomas]

https://www.amazon.com/DOMETIC-33081-SAIL-SWITCH-SMALL/dp/B085MMHB65

 

[DarinH]

I'll vouch for the duct tube removal being the trick (at least for mine). I took it out of my '21 Grandby front dinette, ran the heater off camper battery power, and it stayed lit. Before, it wouldn't stay lit when running off a full charge battery, but worked fine on shore power or with truck idling.

It really bothers me that Dometic would put such poorly designed, temperamental heaters out in the marketplace, AND it bothers me that FWC is using them with so many people having problems with them. WAKE UP FWC - listen to your customers!!

 

[Mthomas]

I mentioned this in another thread somewhere, but I think the core issue is that the furnace being used is a special low amperage design dometic makes. FWC is trying to balance power demands, or rather, power conservation, with staying warm. Dometic is not going to develop a whole new heating system if they can adapt an existing one. I believe that the current units installed in our campers are a low amperage draw unit based off of the Dometic(Atwood in the day)existing product line. A few years ago people complained that their batteries were dead in the AM if they ran the heater all night. The newer system is probably operating right at the limits of heat exchange in order to save electricity. Any slight deviation, poor air flow due to constriction or altitude, or slight contamination of the sail switch causes a fault condition. Clean your sail switch annually, get the updated one as a back up, remove or alter the ducting into the living space if needed and it will work. This area can be frustrating for those having issues, but think of all the cool stuff you can do with your camper and all the remote places you can get too, and remember that because of great communities like this one you do have a fix for the issue.

 

[DarinH]

I mentioned this in another thread somewhere, but I think the core issue is that the furnace being used is a special low amperage design dometic makes. FWC is trying to balance power demands, or rather, power conservation, with staying warm. Dometic is not going to develop a whole new heating system if they can adapt an existing one. I believe that the current units installed in our campers are a low amperage draw unit based off of the Dometic(Atwood in the day)existing product line. A few years ago people complained that their batteries were dead in the AM if they ran the heater all night. The newer system is probably operating right at the limits of heat exchange in order to save electricity. Any slight deviation, poor air flow due to constriction or altitude, or slight contamination of the sail switch causes a fault condition. Clean your sail switch annually, get the updated one as a back up, remove or alter the ducting into the living space if needed and it will work. This area can be frustrating for those having issues, but think of all the cool stuff you can do with your camper and all the remote places you can get too, and remember that because of great communities like this one you do have a fix for the issue.

We shouldn't be the ones having to figure out a fix for the issue. FWC is knowingly putting these defective furnaces out there and leaving us to deal with the problems. And the furnaces aren't covered in their warranty. I took delivery on my brand new Grandby less than 2 months ago and I'm dealing with a temperamental heater. Like others have said, for what they charge for the heater "option", and the overall price of their campers, they should be the problem solvers on this, not their customers.

 

[Mthomas]

I absolutely feel your frustration and I totally agree that FWC needs to make sure that their design accommodates the heater that they are installing. It does seem that something changed with regards to how the grill was mounted and it is affecting some newer builds for some users. I also know that there are only a couple options for heating an RV like ours, and I see complaints on forums about all of them. The only unbiased source I have is an upfitter I know who feels that all of the heating options are problematic to one degree or another. It also seems that there was a design issue with some of the earlier sail switches which Dometic appears to be addressing per earlier information in this thread and the “new” sail switch.

As far as cost, while our campers are not cheap, they are by no means the high end of the range. Consider an earthroamer at 250,000, or an airstream trailer at 150,000, or even a basic sprinter build out for 90,000-120,000, or even a Hallmark at about 10-15k higher for a very similar unit.

My main point was that thanks to information found here, we know how to manage the issues, and can focus on the benefits of owning these cool platforms as opposed to focusing on the occasional frustrations.

 

[Vic Harder]

. The only unbiased source I have is an upfitter I know who feels that all of the heating options are problematic to one degree or another. It also seems that there was a design issue with some of the earlier sail switches which Dometic appears to be addressing per earlier information in this thread and the “new” sail switch.

People are having good luck with Propex Heaters, and Webasto heaters. There are options.

 

[larryqp]

I believe someone either told me or I read it on another post on the forum, that the propex system, which I did install in a previous FWC eagle shell is not RVIA certified, therefore FWC can't use it. I'm not aware if the Webasto is RVIA certified.