Furnace shuts off in cold weather - Montana Owners Club

MOODY · 06-06-2021, 07:06 AM

2020 Montana- Legacy - Dometic Furnace
Furnace with In-Command shuts off in cold weather. Originally shut off with temps below 35 degrees and once temp reached 40 degrees the furnace would start working again. If attempting to start the furnace the blower fan starts, after approx 10 seconds the furnace starts but quits after approx. 10 seconds. The blower fan continues to run and after approx. 15 seconds the furnace will relight but will quit again after approx. 10 seconds. This sequence will repeat itself. The blower fan never shuts off till after 15 min of this sequence. Fuel tnks are full. The fact that the furnace does works all day in temps above 40 degrees and regulator already replaced should rule out any propane issues
The sail switch is clean and has 12 volts from the circuit board to and from the switch.
The voltage from the circuit board to the thermistor is 3 volts. I have been advised the correct voltage is 12 volts.
The dealer after the 1st occurrence replaced the regulator but did not document any diagnosis procedure performed so one can not determine if any proper diagnosis was performed or merely shot gunning the repair process.
I went to the Badlands in 8" of snow and found out I would be vacationing in sub-freezing temps w/o a furnace when i turned on the furnace.

Now with temps in the 70's the dealer is unable to duplicate and wants me to pick up the unit. Montana is saying unable to duplicate - no repairs - wait till i have the unit out again in sub-freezing temps and then take it back to the dealer.

QUESTION - ANY IDEA WHAT PART I MIGHT NEED TO HAVE ON HAND TO REPAIR SAID CONCERN?

ChuckS · 06-06-2021, 08:33 AM

I would have to check and replace (just me) the Hi Limit switch and also remove and check the ignitor gap setting on that furnace... When furnace quits but blower still runs do you hear the tell tale popping sound of ignitor firing? IF so then sail switch is fine and either issue with Hi Limit switch too sensitive or some blockage on the outlet lines causing furnace to over temp

There is also a Service bulletin out that you might want to look at since your issue is temp related at 40 degree weather..

https://static.nhtsa.gov/odi/tsbs/20...53026-9999.pdf

MOODY · 06-06-2021, 08:54 AM

The furnace actually lights and runs for approx. 10-15 seconds but then shuts off. The furnace relights after approx. 15 seconds. Everything is as normal except the furnace shuts off after 10-15 seconds.
I was advised I need 12 volts to all circuits and to all sensors and only having 3 volts present to the thermistor that there is a circuit board failure. Probably a bad solder connection within the circuit board itself.

jsb5717 · 06-06-2021, 09:29 AM

Mine was doing the same thing. Turned out to be the propane regulator. The furnace demands full volume of the regulator output. If the reg is under-performing the furnace won't work correctly even though the other propane appliances will. Mine came with a Fairview Reg. I replaced it with a Marshall Excelsior. It has worked perfectly since.

jcurtis934 · 06-06-2021, 10:24 AM

My furnace started to operate very similar. It would sometimes not work unless both propane tanks were turned on. I pulled out the propane valve/ignitor assembly in the furnace and found some stick bugs in the ignitor assy, but did not fix the issue. My issue was the propane valve in the furnace not being able to supply full fuel demand. I could adjust it to get it to work or adjust the main changeover regulator to get things working...but knew that it was time to replace the valve in the furnace. All is right with the furnace now. Point to be made here is that several things can cause fuel flow issues that can result in this behaviour of the furnace. Unless you know that the work was done with the right tools to diagnose and measure propane pressures, it's hard to know the issue was really found.

MOODY · 06-06-2021, 11:28 AM

Dealer replaced the regulator for this concern - concern still present
Works all day long but quits at night after temps drop to below 35 degrees. Starts working again properly once temps are above 35 degrees.

12 volts to sail switch but only 3 volts to thermistor - anyone know if this is correct or not?

Should have measured voltage to thermistor when working but I was in temps below 35 degrees till I returned to the dealer.

jsb5717 · 06-06-2021, 12:30 PM

I'm just guessing but it could still be the regulator if the OEM replacement is a Fairview which might be responding badly to the colder temps. Only one way to find out so would be nice to have a more comprehensive diagnosis. I suppose it could also be the control board but you'd think they would be able to test that. Wouldn't the control board dictate the voltage to the thermistor? I don't know what the correct voltage should be.

MOODY · 06-06-2021, 02:26 PM

Thanks for the Service Bulletin - Seems strange that there is no diagnosis test or procedure to follow to determine that this is the actual failed component. Is the technician merely to verify the concern and then start this repair without any confirmation of this being the actual failed component. Parts Exchanging without failure verification leads to many, many repeat repairs. If it starts working after this repair did you actually make the correct repair or did it just start working again by itself?
Dealer is unable to duplicate my concern now that it's warmer but this bulletin doesn't provide for a test to verify.
Again thanks for this info - I really appreciate your time

MOODY · 06-06-2021, 02:39 PM

I checked the Marshall Excelsior website - wow do they have a bunch of regulators. Any idea which one you bought?
And thanks for your assistance!

jsb5717 · 06-06-2021, 03:19 PM

This is the one I got

https://www.amazon.com/Marshall-Exce...s%2C522&sr=8-3

Ozarkwoods · 06-06-2021, 05:59 PM

Quote:

Originally Posted by MOODY

2020 Montana- Legacy - Dometic Furnace
Furnace with In-Command shuts off in cold weather. Originally shut off with temps below 35 degrees and once temp reached 40 degrees the furnace would start working again. If attempting to start the furnace the blower fan starts, after approx 10 seconds the furnace starts but quits after approx. 10 seconds. The blower fan continues to run and after approx. 15 seconds the furnace will relight but will quit again after approx. 10 seconds. This sequence will repeat itself. The blower fan never shuts off till after 15 min of this sequence. Fuel tnks are full. The fact that the furnace does works all day in temps above 40 degrees and regulator already replaced should rule out any propane issues
The sail switch is clean and has 12 volts from the circuit board to and from the switch.
The voltage from the circuit board to the thermistor is 3 volts. I have been advised the correct voltage is 12 volts.
The dealer after the 1st occurrence replaced the regulator but did not document any diagnosis procedure performed so one can not determine if any proper diagnosis was performed or merely shot gunning the repair process.
I went to the Badlands in 8" of snow and found out I would be vacationing in sub-freezing temps w/o a furnace when i turned on the furnace.

Now with temps in the 70's the dealer is unable to duplicate and wants me to pick up the unit. Montana is saying unable to duplicate - no repairs - wait till i have the unit out again in sub-freezing temps and then take it back to the dealer.

QUESTION - ANY IDEA WHAT PART I MIGHT NEED TO HAVE ON HAND TO REPAIR SAID CONCERN?

We have the same issue happening but we do not have the command control. In the cooler temps in the morning, or after a rain. I am thinking more like moisture in the burning tube is causing the flame sensor to steam over. Mine will work fine for the rest of the day after several cycles of the solenoid click, flame ignition, flame out after 10 seconds.

For Ss and Gs I just tried my furnace it’s 78 degrees and hasn’t rained for some time in the Black Hills. Furnace worked flawlessly.

Darrel · 06-09-2021, 01:19 PM

I understand that all electric heats stops between 35-45. At that point you need to switch to propane heating.

MOODY · 06-09-2021, 02:38 PM

Darrell
No this occurs on propane. Heat pump works fine down to approx. 35 degrees. I was in the Badlands and daytime temps were approx. 40 degrees and nightime temps went down into the 20's. I would run the heat pump during the day and at night I ended up using plug in heaters. I never did get the propane to come on at all except as described in my complaint. I was in the Badlands for 10 days.
Previous trip the propane furnace would come on after ambient temp was above 35-40 degrees and would run all day but would shut off during the night after temps dropped below 35 degrees. Occurred for 3 days.
I returned to the dealer who replaced the propane regulator. I left 30 days later (without testing) and went to the Badlands.
Sail switch removed & inspected. Clean. Test at 12 volts installed and when the furnace is turned on. 12 volts from the circuit board and from the sail switch.
Tested the voltage at the circuit board to the thermistor - 3 volts - I have been advised the correct voltage is 12.
Returned to the dealer and with temps in the 70's everything is working.
I have been advised to pickup the RV and return when it stop working.

Daryles · 06-09-2021, 03:50 PM

This was documented by Jim Vititow.
Furnace failed in very cold temps.
Jim has a Montana and owns an RV dealership.
One of his techs figured it out by placing the circuit board in the freezer. When it was very cold it would not work. Then they warmed it up with a heat gun. And it would start working.
I had the same thing happen to me camping in January. Furnace wouldn't run. I put a hair dryer blowing on the circuit board and after a few minutes it fired up. Put the cover back on and kept the heat running all night (22⁰F).

There was a video Jim made but I can't find the link now. He mentions it in this link.
Bad circuit board, heat gun troubleshooting. By Jim Vititow.
https://m.facebook.com/groups/274058...6677795389293/

**Carl n Susan** · 06-09-2021, 04:00 PM

Quote:

Originally Posted by Daryles

This was documented by Jim Vititow.

https://m.facebook.com/groups/274058...6677795389293/

Darn, how many Montana related Facebook groups are there? This link goes to the Keystone Montana RV Owners Group, and I am a member of the Montana RV Owners Group. I have heard of models specific Montana groups. No wonder people have trouble with FB.

MOODY · 06-09-2021, 05:19 PM

Daryl

Thanks for the info - bad link to video but at least I have a name of someone I can try & run down

Kevin

Daryles · 06-09-2021, 07:24 PM

Sorry guys, I don't know why these FB links never work.
The post is by Jim Driscoll, dated February 24, 2020.
Hopefully you can search on that and it will pop up.
Anyway, you can troubleshoot the control board by firing up your furnace, verify its working properly.
Then removing it (take pictures first of the connectors) and putting it in the freezer for a couple of hours. Then put back in the furnace and see if it fires up. If not use a hair dryer to warm it up. If the furnace fires up you have one of those defective boards. Jim went through several bad ones brand new still in the box.

**Carl n Susan** · 06-09-2021, 07:56 PM

Quote:

Originally Posted by Daryles

Sorry guys, I don't know why these FB links never work.
The post is by Jim Driscoll, dated February 24, 2020.
Hopefully you can search on that and it will pop up.

The basic problem is you have to be a Facebook user and have joined the Group that the info was posted in. Facebook is a closed society, unlike the MOC, so info stored there isn't visible unless you jump through all the hoops.

MOODY · 06-09-2021, 08:49 PM

Hopefully I can get the dealer to attempt this - it's still under warranty. I called Montana - TWICE - Monday and again on Tuesday and each time - WE WILL GET BACK TO YOU - still waiting!
I forwarded this info to the advisor,
And THANKS

Ozarkwoods · 06-12-2021, 06:55 AM

I am having the same issue but no command panel. This has been something that has progressed from working fine to an occasional hiccup to this morning the furnace attempting to start it took 12 cycles of the fan purge, solenoids clicking and the ignition. As the 12 attempts progressed the burner would kick in a bit longer each time ranging from a two second burn, ten second burn, 15 second burn, 30 second burn to the last attempt when it ran constant. I have had it off for 10 minutes now and started it back up, worked fine. This morning it is 53 degrees with heavy dew on the ground. I have not run the furnace for a couple of weeks between that time we have had two heavy rain storms. I am thinking it has something to do with moisture.

The sound of the burner to me sounded like it was not a strong flame during this process. Kind of like spitting and sputtering.

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