Strange furnace problem

[davidmurphy02]

Originally Posted by Gasguy

I would think you would be safe with that. Mark the preadjusted position with a sharpie & a picture for reference. If you started with 1/4 turn increments.

Sharpie is ready, that is what I will do.

[davidmurphy02]

Well, the plot thickens....down at 5000 feet and it has been fine for almost a week but this morning would not ignite. Multiple resets and retries failed, then an hour later I tried again and it finally ignited.

It is sure seeming like I have some problem in the ignition process. Does anyone have a handy parts diagram, is the electronic igniter accessible from the outside panel? Are there any other possible mechanical components in the furnace that could be amiss?

[rubicon327]

Originally Posted by davidmurphy02

Does anyone have a handy parts diagram, is the electronic igniter accessible from the outside panel? Are there any other possible mechanical components in the furnace that could be amiss?

If you go to https://www.edometic.com/ you can choose Atwood Furnaces, then choose Small Atwood Furnaces and then choose your model number which should be DFSAD12###. Link to parts diagram can be found at upper right of each page. I don't believe the ignitor is accessible from the outside panel.

Wiring diagrams are available in the manual:
https://epi.dometic.com/externalasse...1143_81452.pdf

If you consider replacing the control board I would look into the universal ignitor board (UIB-S) by Dinosaur Electronics.
https://www.dinosaurelectronics.com/UIB_S.htm

[davidmurphy02]

Originally Posted by rubicon327

If you go to https://www.edometic.com/ you can choose Atwood Furnaces, then choose Small Atwood Furnaces and then choose your model number which should be DFSAD12###. Link to parts diagram can be found at upper right of each page. I don't believe the ignitor is accessible from the outside panel.

Wiring diagrams are available in the manual:
https://epi.dometic.com/externalasse...1143_81452.pdf

If you consider replacing the control board I would look into the universal ignitor board (UIB-S) by Dinosaur Electronics.
https://www.dinosaurelectronics.com/UIB_S.htm

Thanks! My next board will be Dinosaur, but I am inclined to think that the odds I have two bad boards are low since the intermittent ignition problem occurred with both. It has now occurred at both high and lower altitudes so doesn't seem like an altitude issue. Fridge and water heater are doing fine so it doesn't seem like a propane regulator issue. I am running out of hair to pull out.

At this point I am just hoping it stays intermittent to get us through cold nights at 8000 feet at Great Sand Dunes in a week or so. Next stop from here is Dead Horse Point, won't be cold there, and after the sand dunes we'll be heading south back to Texas. Once we are home I can tear the furnace apart if I need to...sigh.

[rubicon327]

Originally Posted by davidmurphy02

Thanks! My next board will be Dinosaur, but I am inclined to think that the odds I have two bad boards are low since the intermittent ignition problem occurred with both. It has now occurred at both high and lower altitudes so doesn't seem like an altitude issue. Fridge and water heater are doing fine so it doesn't seem like a propane regulator issue. I am running out of hair to pull out.

At this point I am just hoping it stays intermittent to get us through cold nights at 8000 feet at Great Sand Dunes in a week or so. Next stop from here is Dead Horse Point, won't be cold there, and after the sand dunes we'll be heading south back to Texas. Once we are home I can tear the furnace apart if I need to...sigh.

David: What is the return air path? Is it just the remaining free area of the grille around the supply duct? If you have the lower cabinet door underneath I wonder if that cabinet area communicates to the furnace return and if so if keeping that open makes any difference. A restricted air path could be causing intermittent issues with the sail switch making.

[TZBrown]

Do you still have the flexible duct on the furnace out to the room?
Because of the flex hose the outlet air flow can be restricted somewhat
Maybe try removing the plastic grille and run the furnace to see if it would make a difference.
I replaced the flexible duct with a piece of metal round duct, cut to fit. It helped air volume a bunch

[davidmurphy02]

Originally Posted by rubicon327

David: What is the return air path? Is it just the remaining free area of the grille around the supply duct? If you have the lower cabinet door underneath I wonder if that cabinet area communicates to the furnace return and if so if keeping that open makes any difference. A restricted air path could be causing intermittent issues with the sail switch making.

Return air is just the front grill, no path underneath. But sail switch is giving the all clear every time and then it is the ignition process that is failing. Wouldn't light in several tries yesterday evening, then finally did and cycled all night until 5am when it failed once, then worked again after that.

[WRGooding]

Dam, sail switches! Want to make money come up with a replacement. Could be a simple as it is stuck. This happens due to a bump in the road or just vibration. Very little clearance on the compartment; may start then not start.

Any new system replacement ideas are appreciated.

[Flyfisherdan]

It could be the high limit switch is in the process of failing and gives a faulty signal to shut down, or keep the furnace from igniting. I just bought a back up OEM switch from Panther RV in WA for about $23. Hope you discover the source of the problem.

[davidmurphy02]

Originally Posted by Flyfisherdan

It could be the high limit switch is in the process of failing and gives a faulty signal to shut down, or keep the furnace from igniting. I just bought a back up OEM switch from Panther RV in WA for about $23. Hope you discover the source of the problem.

Ah, yet another possibility. Were you able to change out the high limit switch through the outside compartment? Do yo happen to have a link to that part at Panther?

[rubicon327]

Originally Posted by davidmurphy02

Ah, yet another possibility. Were you able to change out the high limit switch through the outside compartment? Do yo happen to have a link to that part at Panther?

David: My guess is since Flyfisherdan said "back up" switch that he didn't actually replace his. From the looks of where the high limit is situated you should be able to replace from the outside compartment. Also here is a link to the high limit switch that should work with the Dometic DFSAD series.
https://pantherrvproducts.com/dometi...-limit-switch/

[davidmurphy02]

Thanks Rubicon. The diagram and photo are not my furnace, but I have the link you posted earlier and can get it there.

[rubicon327]

Originally Posted by davidmurphy02

Thanks Rubicon. The diagram and photo are not my furnace, but I have the link you posted earlier and can get it there.

Yes. Should have mentioned that. I don't have your exact furnace model # but it should still be in the location I show.

[Flyfisherdan]

Dave, Rubicon is correct that I haven't yet installed the replacement high limit control yet. Also, my furnace was the year before they switched to the new outside access panel version. I am a bit of a boyscout like you, in that I have a backup Dinosaur board, sail switch, and high limit control as spare parts in the event they are needed. If I ever have problem and need to pull the furnace out, I will likely replace all three at the same time and then do some trouble shooting afterward to find out which part is bad and keep the others as "used" back ups. Finding electric gremlins can be very frustrating. I hope you determine the issue soon.

Dan

[Flyfisherdan]

Rubicon, Thanks for sharing the link with Dave for the high limit switch. That is the exact switch I purchased from Panther for my AFSAD 12 furnace.

Thanks,

Dan

[Paul Dean]

Originally Posted by Gasguy

Typically propane tank regulators are fixed adjustment. If they can be adjusted, remove the threaded cap on the regulator body & turn adjustment clockwise to increase pressure. The size of the orifice on the burner manifold determines the amount of fuel that will flow to the appliance. There is also a orifice inside the regulator body. Everything is sized for the atmospheric pressure & altitude the manufacturing company determined the appliances will operate at.
If you do crank it up to get more fuel pressure count the turns & set it back to pre adjustment when you get to your normal operation altitude. Leaving the appliances in a over-fired condition can cause flame impingement, carbon monoxide conditions & premature failure. A manometer should be used to check the pressure if you suspect faulty regulator.
Should note as well the pressure could need to be adjusted down a bit to compensate for lower oxygen available at altitude causing to rich a fuel mixture.

Wow, lots to learn in this thread! Looks like I'll be getting a manometer, backup sail switch, control board, and high limit switch.

This video is really helpful re. how to do the pressure test and adjust the regulator.

[davidmurphy02]

An update in my ongoing furnace saga. When we got the trailer I added window screen behind the front grill to keep cat hair out because of all the sail switch problems being reported back then. I removed it a few days ago, it was dusty su I just cut it off in case it was contributing to an airflow problen.

The first time I tried the furnace with the screen removed it failed ignition 3 times and locked out yet again...drat! However, in the several days since then it has operated all night without failing. On several occasions it has ignited on the second or third attempt but did keep going without intervention.

Weather has not been very cold and we have been around 5000 feet. Moving today to Great Sand Dunes at 8200, 27 tonight so it will get a better test. I have tried to check the LED on the circuit board for error flashes several times but each time I have gone out and removed the exterior panel and then had Mary start the furnace while I watched the LED, the furnace ignited. Maybe I just need to let her turn it on from now on

[Mike G]

Sounds like you just need to do a "hail Mary" every time!

[davidmurphy02]

Hopefully a final update to my furnace saga. After several cold nights at 8200 feet it has continued to work fine. Apparently removing the window screen filter on the intake did the trick.

In the course of the past few weeks I have learned a lot about every aspect of the furnace and benefited from all of your tips, suggestions, and collective wisdom. I originally added the screen filter to protect the sail switch but then had sail switch failures anyway. Since replacing the sail switch with a new one is have had no further sail switch issues.

I still love this little furnace, it's quiet, very efficient and heats the trailer well. Apparently the low power blower motor that makes this efficiency possible is very sensitive to anything that impedes the airflow even a little so I will be watchful if it ever acts up again. The screen I had added was only on the return air intake, not the round output vent, but I still may look at replacing the flexible duct with a metal one as others have done to make that air passage more smooth.

Thanks again for all you help everyone!

[rubicon327]

Originally Posted by davidmurphy02

After several cold nights at 8200 feet it has continued to work fine. Apparently removing the window screen filter on the intake did the trick.

Nice work! Hope you've got this solved permanently. In the meantime you have learned a lot and are ready to troubleshoot if you do happen to have any future issues.