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  1. #1
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    Dometic Furnace Won't Stay Lit

    We just bought a brand new 2023 Imagine 2600RB

    We tried the furnace (Dometic) for the first time and this is the sequence of events:

    1. Setting for "Heat" on the Furrion control
    2. The blower starts and stays on for the entire process.
    3. Igniter clicks
    4. I hear the roar of the flame for anywhere from 2 seconds to less than a minute.
    5. The flame goes out.
    6. After approximately 15 seconds the igniter clicks and I hear the roar of the flame again.

    Steps 5 and 6 keep repeating (I've let this go for as long as 20 minutes).

    1. The 2 - 20 lb. LP tanks came filled from the dealer. I lifted them and they feel full.
    2. I'm plugged into shore power and batteries are at 100%.
    3. I tried the range top with all 3 burners lit and that worked.
    4. I tried all 3 positions of the tank selector switch (not sure what it's called). The middle position as well as pointing to each tank.
    5. I have tried this 3 times now. Two times was at night (colder temps) and it seemed worse. When I tried it in the warmer part of the day the flame seemed to stay lit longer. In fact it ran long enough to reach the set temperature for several cycles.
    6. We are in New Mexico at 5150 ft. elevation.

    I am not at all mechanical but I wonder whether the regulator is not allowing enough pressure and the furnace is shutting off due to low pressure.

    If this is the case, it seems that the regulator functions worse at colder temps.
    Last edited by dgcksanders; 11-29-2023 at 10:38 PM.

  2. #2
    Big Traveler
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    Because it keeps re-igniting...I'm tending to think T-stsat. Usually if a furnace stops in a manner other than the t-stat telling it to stop it will lock out immediately or after up to three tries depending on t-stat brand. So I 'think' the t-stat is telling it to stop.
    I would first take the t-stat off the wall and check the wiring connector at the back, make sure everything 'appears' good. If you are handy with a meter, you could turn up the t-stat and verify the 12v signal to call for heat comes on and stays on. Or you could try to get your dealer to supply a good spare to try?
    Before buying a t-stat though, check the usual suspects. I would check the furnace for any loose wire connections. Reseat the MB connections, and remove and re-attach the propane connection. If you have compressed air available..blow out the burner tube.
    I don't think 5000' is high enough to cause burner issues...but I could be wrong...did the furnace work fine at lower elevation?
    Last edited by Scott'n'Wendy; 11-30-2023 at 06:14 AM.
    2018 Dodge 3500 6.7 Cummins SRW w/Aisin
    2021 Reflection 303RLS
    New to RV'ing since 1997

  3. #3
    Setting Up Camp
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    Sounds like the sail switch might have some debris on it. Remove the furnace cover, and there should be a small rectangular plastic piece, held in by 2 screws near the middle of the blower body that has a small wire or 2 going to it. Remove that piece and gently blow it of or check for something preventing it from flapping. The smallest piece of debris can keep this part from functioning. It needs to flap in the breeze the blower make to tell the furnace it is working.

    For the propane, keep the regulator to either the left or right, not middle.
    2023 Reflection 324MBS
    2020 Sierra 2500
    Colorado Springs, CO
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  4. #4
    Setting Up Camp
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    Sounds like a sail switch, as The Bruck Fam stated. It’s a good idea to have an extra one on hand. If you travel with a pet, the hair will stick to the switch and cause it not to ignite. Several you tube videos on this.
    Jason & Celia-Texas
    2019 GD Reflection 337 RLS
    2020 GMC Denali, Dually
    Pungo Kayaks,Lectric E-bikes

  5. #5
    Big Traveler
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    Quote Originally Posted by Jason-Texas View Post
    stick to the switch and cause it not to ignite. Several you tube videos on this.
    That's why I don't think it's a sail switch. If the sail was faulty or not making, the furnace would not ignite. But it does.
    2018 Dodge 3500 6.7 Cummins SRW w/Aisin
    2021 Reflection 303RLS
    New to RV'ing since 1997

  6. #6
    Seasoned Camper
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    Since it is a new unit I would look for installation issues;
    -Propane: does the water heater run on propane ok (ie, a high-demand propane appliance). This should rule out the regulator. Also look for kinks in the propane hose feeding the furnace.
    -Airflow obstructions: is there good airflow at the outside exhaust port? Is there good airflow at the vents when the unit is running? Usually the vents closest to the furnace will have the most airflow.
    -Loose wires are key. You might have to remove the panel in the basement that will reveal the furnace. Check(light pull test) every crimp cap for each of the three wires coming out of the furnace as far back to their source as you can.
    -The next step would be to look for mud dauber nests in the exhaust or spider webs in the burner area. You will have access to these areas when you remove the cover to the furnace (if you blow out the burner tube)
    Last edited by bjlakatos; 11-30-2023 at 01:02 PM.

  7. #7
    Seasoned Camper
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    I am more inclined to think you have an issue at the exhaust/intake connection from furnace to wall vent connection ..

    Sail switch is not the issue ..

    The other item I would be looking at is Lully the burner assy and clean ignitor and flame sensor and set the gap .. this is a fairly simple task if you have an outside furance panel access..

    Plenty of good videos showing how to do this on a; AFM35 or DFM35 series furnace

  8. #8
    Setting Up Camp
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    With 20 # tanks you will lose pressure with both altitude and cold. You have said it works better in the day when it is warmer so this may be the issue. I've had this issue on previous trailers when in very cold weather.

    I found a chart from a furnace training manual couple of years ago which says that at 0 degrees F a 20 # tank has half the BTU's than at 20 degrees F. If it is only 50% full the BTU available will reduce even more so that you may not get ignition. The altitude will further reduce that pressure however I do not know the calculations on how much affect that will have. You can check if it is low pressure due to cold putting warming up the tank you are using with a heat gun or some other kind of heat onto the tank. If the problem goes away, then you've found the issue. Alternatively, you can wait until you get back to warmer conditions and a lower elevation to see if it lights normally.

    Good luck resolving this and hopefully you don't get too cold.
    Ian
    2015 Reflection 29RES
    2013 RAM 3500 HD long box SRW
    British Columbia, Canada

  9. #9
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    furnace won't stay on more than 20 sec

    Quote Originally Posted by The Bruck Fam View Post
    Sounds like the sail switch might have some debris on it. Remove the furnace cover, and there should be a small rectangular plastic piece, held in by 2 screws near the middle of the blower body that has a small wire or 2 going to it. Remove that piece and gently blow it of or check for something preventing it from flapping. The smallest piece of debris can keep this part from functioning. It needs to flap in the breeze the blower make to tell the furnace it is working.

    For the propane, keep the regulator to either the left or right, not middle.
    I have a new 2024 Imagine 16ML with a furnace that won't stay lit. Furnace worked initially, but now no. Blower comes on, then furnace shuts off after 20 sec or so.Other gas appliances working fine, shore power is fine. This is the same behavior as my previous trailer (also new) that had a bad sail switch. Can I look at this myself? The outside cover appears to be caulked on & I was hesitant to remove it. The trailer is only 6 weeks old, so I can't believe the sail switch is dirty.

  10. #10
    Setting Up Camp
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    Quote Originally Posted by bjlakatos View Post
    Since it is a new unit I would look for installation issues;
    -Propane: does the water heater run on propane ok (ie, a high-demand propane appliance). This should rule out the regulator. Also look for kinks in the propane hose feeding the furnace.
    -Airflow obstructions: is there good airflow at the outside exhaust port? Is there good airflow at the vents when the unit is running? Usually the vents closest to the furnace will have the most airflow.
    -Loose wires are key. You might have to remove the panel in the basement that will reveal the furnace. Check(light pull test) every crimp cap for each of the three wires coming out of the furnace as far back to their source as you can.
    -The next step would be to look for mud dauber nests in the exhaust or spider webs in the burner area. You will have access to these areas when you remove the cover to the furnace (if you blow out the burner tube)
    Iíll second the check wiring advice. I had this exact same problem and it was caused by a loose ground wire, the sheet metal screw that grounded one of the connectors was not tight. Tightened it up and the furnace worked consistently after that.
    Tom R
    2022 Reflection 150 Series 295RL
    2019 Ford F250 Super Duty XLT 6.2L

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