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Old 10-31-2022, 02:59 PM   #1
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2022 Micro Minnie 1708FB Furnace issue at sub freezing temps

Good afternoon folks!
Ran into an unpleasant situation this past weekend. I was boondocking in the high country this past Friday night. Furnace worked well at 62-degree thermostat setting through most of the night. At around 0430 inside of the trailer was 22-degrees while outside was a bitter 7-degrees. A quick conclusion was obvious the furnace wasnít igniting, but the fan would run. Reset the furnace by turning the thermostat off & on again. Fan came on, but no flame ignition. The furnace cycled twice like this. Checked the propane level and it was fine. Lit the cook top to confirm there was propane and pressure. Cook top worked at full throttle just fine. Long story short, packed up and headed back for home. Once at home I heard the furnace working and confirmed the trailer was 60 degrees & warm inside.
Iím sure its cold weather/altitude related as I canít replicate the non-igniting here at the house. For reference, the temp at camp was 7-degrees, altitude at camp was 8878-ft. Home temp was 30-degrees with an altitude of 7500-ft.
Can someone tell me if this is related to propane flow at cold temps, or possibly the sail switch, or something else?
Thanks!
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Old 10-31-2022, 03:04 PM   #2
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My furnace did this a little over a year ago. I took it into the independent shop I use. They diagnosed it as a bad circuit board with an intermittent problem. They replaced the circuit board and I've had zero issues since.
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Old 10-31-2022, 04:44 PM   #3
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Hey-

Does the normal cooking stove light up?
Fridge running on propane ?
This would eliminate the propane regulator.

If regulator seems Ok I’d pull fuse to heater , wait a minute and plug it back in.
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Old 10-31-2022, 05:15 PM   #4
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Just to chase down and cross off one itme, did you do the "stove works" test at or near the time when the furnace was failing? Wondering if the timing was such that the propane was semi-frozen up to cut the pressure too low but you waited until light and tested then which let the stove work?
Pressure when cold and at high elevation can get funny and fool us if we are a bit sleepy!

Possible a funky sail switch? Is your furnace located so getting to the sail switch is difficult to impossible?
On a motorhome, with the furnace back handy to get to, a jumper across the sail switch can sort out if it is a problem. Just a small micro switch with a sail attached, so putting a jumper across will tell if the sail switch is not letting power go to the gas valve.
Also if where you can get to it, listen and feel the gas solenoid/valve to see if it is trying to click open?

Ideas to try without much to back the idea!!
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Old 11-01-2022, 09:34 AM   #5
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The cooktop was fired off at camp when the furnace wasn't working. -And come to think of it, the fridge DID sound a check alarm (beeping) when I arrived back at home (when the furnace was back to running again.
Thanks for the directions on this, I have some new items I can check out. Sincerely appreciated! Have a great day!
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Old 11-01-2022, 10:50 AM   #6
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Just as a way to avoid going to repair as long as possible, there might also be something cheap to test out. Do you know about solenoids being an electrically operated valve? That means there is a moving part which has to be opened by the magnetic coil.

So what if the moving part is not moving as easy when it gets super cold? Cold works on lots of things and makes them work less well!

So if you are able to get to the solenoid at the furnace that opens, you might look at how it is progressing through the order.
You are getting the fan to come on, showing the thermostat and wiring to the furnace are ok.
That airflow needs to be enough to move the sail on the switch to close the microswitch.
Bugs building nests in the vents is a common failure but that doesn't sound right when it works and stops during really cold---bugs not out and about! Maybe during the summer, though so I put screens over all the vents!
When that switch closes, the board senses it and then sends a signal on to the gas valve telling it to open. If you can get a meter on the leads to the solenoid/gas valve, you may be able to see the voltage jump up. If not, the board may become suspect!

But if you see voltage go to the solenoid but it not move, try whacking it with a screwdriver handle, etc. as a trick to see if it jars loose! If it comes loose and gas flows to light, then the gas valve is suspect??

But that may not be it either, so if you hear, feel, or smell gas moving, check the igniter is getting the signal to ignite that gas. Some have a "clicker" like a gas grill and others may have a glowing hot item to light it.
Warning:
If you have gas flow, don't let it run too long without ignition so that you collect too much and it goes WHUMP! NOT good for your eyelashes----or nerves!

Good luck!
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Old 11-11-2022, 08:47 PM   #7
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I recently had the same problem on my 2021 2100BH and it turned out to be something as simple as a fuzz ball that had accumulated on the sail switch inside the blower housing. There is no filter on the air intake of these furnaces so it sucked in debris that was left inside the furnace compartment during the manufacturing process.

My scenario was the same as yours as the furnace worked again (for a while) after moving the trailer.
It also would not fire up when I was boondocking and the battery voltage dropped to 12.2 Volts.

My theory is that the lower voltage caused the blower to spin at slightly slower RPMs and there was not enough air speed to push on the sail switch with the fuzz ball interfering with proper activation. OR.....after towing the trailer the jarring dislodged the fuzz ball enough to allow the sail switch to work properly.
Since I already had the furnace out I went ahead and put in a new sail switch. ($10 on eBay, $40 from the stealership) The installation of the switch was a piece of cake BUT removing the furnace was an 8.5 on a PITA scale of 1-10. There is just no room in there to maneuver things around inside the furnace compartment due to the compact design of the Minnies. If you do tackle this yourself beware that there is a small duct on the side of the furnace that runs down to the underbelly.

Unfortunately, the only way to find the model/serial numbers of your exact furnace is to pull it out as they are not listed in any of the manuals that came with the trailer. If you do pull it, don't forget to snap a pic of the numbers and write down for future reference.
The start up sequence of these Dometic furnaces are, in my amateur terminology:

1. Blower starts and runs approx. 10 seconds

2. a faint metallic-sounding "clunk" (the gas solenoid opening)
3. the "tick tick tick tick" of the igniter
4. the faint "poof" sound of ignition
5. heat
If gas is flowing properly and there is no "clunk" followed by "tick tick tick" the odds are very high that it is the sail switch.
If the red LED on the circuit board flashes once followed by a 3 second pause, this indicates a problem with the sail switch.
Good Luck!
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Old 11-27-2022, 11:50 AM   #8
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Hope everyone had a great Thanksgiving holiday. I wanted to pass along my appreciation for the responses here. Getting some time off this coming week and will check the sail switch.

This past few weeks however I did stumble on something I think worth mentioning to the community out there. We had a cold snap here in Conifer where the temps again reached single digits. The following couple of days the temps slowly raised back to normal 30-40F. During those transition days I saw the regulator was showing “Red” in the window. I worked the tank change over switch to no avail (confirming I did have good tank pressure). Finally when the temperatures reached mid to upper 30s the regulator showed green again. I took that as serious susceptibility to cold temps and mechanical freezing of something in the regulator.

Yesterday I ventured out to the local camping world store and spoke with a technician. He confirmed that these regulators have no guarantee of functioning at colder (below freezing) temps. No big earth-shattering news there huh... He did however confirm in 2018(ish) through 2020 there was a recall on LPG regulators. The date of manufacture did include some of those trailers built in 2021 and sold as 2022. He couldn’t confirm weather mine was affected as I didn’t have my date of manufacture with me at the time. Given this tho, and that it directly corresponded with my regulators behavior, I ordered a new one.

Interesting thing trying to really understand the best, robust RV LPG regulators. After reviewing many internet sites and looking and what makes & models followed a trend of being towards the top of the list I settled on this one.

JR Products 07-31525 Compact Low Pressure Two-Stage Automatic Changeover Regulator, White

I selected this one primarily because it specifically mentions higher flow rates to improve cold-weather performance. It will be delivered later this week and after I monitor it in the upcoming colder months I’ll follow up and let folks know how well it performed.

Thanks again for all the input – this forum and community is really helpful!
Have a Great Day!
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Old 11-27-2022, 01:47 PM   #9
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Quote:
Originally Posted by Gunny Rio View Post
Hope everyone had a great Thanksgiving holiday. I wanted to pass along my appreciation for the responses here. Getting some time off this coming week and will check the sail switch.

This past few weeks however I did stumble on something I think worth mentioning to the community out there. We had a cold snap here in Conifer where the temps again reached single digits. The following couple of days the temps slowly raised back to normal 30-40F. During those transition days I saw the regulator was showing ďRedĒ in the window. I worked the tank change over switch to no avail (confirming I did have good tank pressure). Finally when the temperatures reached mid to upper 30s the regulator showed green again. I took that as serious susceptibility to cold temps and mechanical freezing of something in the regulator.

Yesterday I ventured out to the local camping world store and spoke with a technician. He confirmed that these regulators have no guarantee of functioning at colder (below freezing) temps. No big earth-shattering news there huh... He did however confirm in 2018(ish) through 2020 there was a recall on LPG regulators. The date of manufacture did include some of those trailers built in 2021 and sold as 2022. He couldnít confirm weather mine was affected as I didnít have my date of manufacture with me at the time. Given this tho, and that it directly corresponded with my regulators behavior, I ordered a new one.

Interesting thing trying to really understand the best, robust RV LPG regulators. After reviewing many internet sites and looking and what makes & models followed a trend of being towards the top of the list I settled on this one.

JR Products 07-31525 Compact Low Pressure Two-Stage Automatic Changeover Regulator, White

I selected this one primarily because it specifically mentions higher flow rates to improve cold-weather performance. It will be delivered later this week and after I monitor it in the upcoming colder months Iíll follow up and let folks know how well it performed.

Thanks again for all the input Ė this forum and community is really helpful!
Have a Great Day!
Gunny, appreciate your posts - in my own world of failing heat from a recent shakedown cruise it wasn't due to an issue with gas flow but rather an electrical issue (now solved via a simple fuse).

But, your experience gives me some good knowledge because as I'm planning future winter camping trips, particularly west of the Mississippi, I didn't think about the combination of altitude and cold and the potential impact it might have my regulator(s).

You've given me another item on the checklist to ensure is gtg before heading out - thanks!

V/R
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Old 11-29-2022, 01:56 PM   #10
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Quote:
I recently had the same problem on my 2021 2100BH and it turned out to be something as simple as a fuzz ball that had accumulated on the sail switch inside the blower housing
Same issue here. The first time getting the furnace out is a PAIN but I can do it in about 5 mins now. The other item to note is the ON/OFF/Reset switch. If you're not getting any fan at all you can reach way in the back and see if toggling that switch gets you going again. It's on the top of the unit all the way above where the exhaust goes out the exterior.

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Old 12-01-2022, 04:44 PM   #11
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Howdy folks,

Well the sail switch seemed clear of any debris or something that would impede its movement.

The new regulator arrived yesterday. (it was 21-degrees F yesterday when I installed it). The old regulator was still showing red in the change-over window even after closing the tank valves, disconnecting the hoses to let the pressure off, and reconnecting & opening the tank valves back up.

After installing the new regulator, the change-over window immediately showed green. It took a few minutes to re-fill the lines, but the cooktop and furnace worked as they should. This week will be warmer here in the Colorado hills, but I'll keep watching this close - I doubt it will take too long before we're really cold again.

For this thread, and for now, I'm putting the root cause right at a faulty regulator. Once we get down into colder temps I'll post another follow up.

Thanks all for the insights and support!
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Old 12-04-2022, 12:26 AM   #12
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Many RVers have experienced freezing of their propane regulators at high altitude and sub-freezing temperatures- they have had success with placing a 60W lead light below the regulator inside the propane cover. If you donít have shore power (120AC) you can use a small 12V heating mat placed at the top of the propane cover close to the regulator.
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