Dometic furnace problems

[SLS5964]

Hello fellow Rv'ers. Hoping someone has had this issue cause CW is certainly no help, LOL, yah big surprise.

Ive got a 2019 Keystone Cougar 29 RLD. We are FT Rv'ers so getting my rig in the shop is very difficult for any warranty work.

We've had NO issues with our furnace since we got the Cougar. BUT, yesterday we needed the heat. The fan started like always, then the click and fire in the furnace lit for about 10 secs and then went off. I've looked into everything, gas/thermostat setting/breaker/15 amp fuse. All working fine. The manual suggested bleeding the gas lines by using the burners, and then try the furnace did that. The water heater works just fine, so no air in the gas lines.


I located the furnace under the fridge, but there's no reset or switch to turn off/on. I've tried changing temps on the thermostat and leaving the system on auto. occasionally the blower comes on, but not the fire.

The Dometic user /Installation manuals are not help, as I have no clue which modal number. Even you tube doesn't cover this.

Any suggestions or help are appreciated.

[richardcoxid]

Sounds like the flame sensor (FS) is burnt out. When the system is working properly the FS thermocouple when heated sends a signal to hold the main gas valve open. If the FS is not functioning properly (not heated by the flame or burnt out) the safety circuit will shut the main gas valve.

The flame sensor is a piece of metal about 3-4” long, 3/16” diameter placed about 1/2” above the burner flame with two wires coming out the opposite end. A more or less a standard low $ item available at any Heating/A.C. repair shop, maybe HD/Lowe’s etc

[SLS5964]

GM, I appreciate the response. I'll keep the suggestion in mind. My biggest problem is that Keystone put my furnace in a place, I can't even get at the guts of the furnace, LOL. It's under the fridge behind a panel, which is fine. BUT, then all the vent tubes are front and center. All I can see is the gas supply line and the wiring at the very back. I believe they installed it before they installed the fridge.

I'm mechanically inclined, so working on things isn't a prob. Just getting to it, LOL. Have you heard or seen situations like that. And there's no outside access.

thanks again for the suggestion,

steve

[Old-Biscuit]

That louvered panel under fridge is the furnace return air vent
It should be removable to allow furnace access




Spark electrode is used for generating a High Voltage spark to ignite flame AND is also used from flame proving detection
(Not a thermocouple)


DC is applied to gas valve while spark electrode if firing...for 6-8 seconds. Then if flame generated signal is not sensed by circuit board it shuts down DC to gas valve so raw fuel doesn't accumulate




What is furnace Model?

[charliez]

Probably just a dirty flame sensor, not a bad one. Propane can leave a white residue on it and sometimes they are not installed well into the flame. So when they are clean they are close enough but when they get dirty they are not. Unfortunately, you have to put your hands and eyes on it to know. Its not as bad as you think. I would pull that cover off and look into pulling th whole box out. i'ts not that bad, then put it on a table and look at the burner area. Clean and adjust that flame sensor as needed. Make sure you have screens on the outside of the vents so nothing can get in it and make a little nest. That will stop them too.



There are diffent shapes. You can look on Amazon for rv furnace screen and pick the one that fits yours.




https://www.amazon.com/TOODOO-Flying...s%2C154&sr=8-4




https://www.amazon.com/Miady-Furnace...-1-spons&psc=1

[foundwaldo]

I have a Coleman and it is doing the same thing. Mine is weird though. It seems to work perfectly sometimes and other times it fails. There should be a vent on the outside for it somewhere with an access panel. Mine is right next to the hot water heater. Behind the panel I found a reset switch, and also found out after 3 tries it would go into a lockout mode. Then if I left it on it would try again after 30 minutes. Here is a picture of mine.

You can see the black switch to the left side that is my reset switch.

[CA Harts]

I had this same type of issue with my Atwood furnace, looks same as the picture in above post. I had a dirt in the sail switch. I removed the outside panel then removed 4 screws on blower motor to access the sail switch. I used a vacuum to clean this out and system ran fine after that.

[SLS5964]

sorry , it's been a bit reposting about this issue, the internet where we were "SUCKED".

I went to a local RV dealership that is keystone certified, and finally got some answers, LOL. Actually had a tech take me out to another Cougar 29 RLD. I already knew about the access panel below my fridge, and had taken it off. that's how I knew "Nothing" is visible or accessible, LOL. He showed me that you have to remove the entire unit to get at the sensors and parts. it sits on a piece of 1/2 ply wood with two screws at the front. the you must remove the front 3 vent tubes and twist off the 3 on the side. And, then take off the gas line. then you can slide out the unit and do the work.


he wasn't very nice about keystone engineers regarding this, LOL.
Anyway, luckily it's not winter, and we are using a space heat if needed.


Appreciate all the helpful hints, but, it's not getting fixed right now, LOL.