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  1. #1
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    Suburban SF-35Q furnace problem

    Have a Suburban SF-35 furnace issue in our 2018 Solitude 384GK. When tstat request is made furnace cycles on normally. Trouble is a constant flame on/flame off situation. Monitoring heat outlet temp, burner flame is on till temp reaches 160F. Then burner cycles of till temp drop to 110F and then back on till outlet temp reaches 160F again. Back and forth till room temp finally reaches tstat setting. Takes forever to warm up trailer.
    I’ve tested furnace operation on another identical trailer. Outlet temp stays around 165F till tstat is satisfied.
    Seems to me a weak limit switch. Anyone else have this problem?
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  2. #2
    Site Team Second Chance's Avatar
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    Sounds like a bad limit switch on the furnace to me. We've had this problem on another RV.

    Rob
    U.S. Army Retired
    2012 F350 DRW CC LB Lariat PS 6.7
    2020 Solitude 310GK-R, MORryde IS, disc brakes,
    Sailun LRG tires, solar, DP windows, W/D
    (Previously in a Reflection 337RLS)
    Full time since 08/2015

  3. #3
    Seasoned Camper
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    Here is a link to a Suburban SF-35Q tune up kit and all of the parts.

    https://pdxrvwholesale.com/products/...5q-tune-up-kit
    Kevin and Jennifer
    2016 RAM 3500 Laramie Mega Cab CTD Aisin 4x4 SRW
    2019 Reflection 28BH (Built 2/2019)
    - 78" Theater Seat, Second AC, Dual Pane Windows
    - Sailun 235/85 R16 Tires
    Blue Ox Super Ride BXR7200 with a Demco Factory Prep Bracket 6099

  4. #4
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    Quote Originally Posted by Kevin2282 View Post
    Here is a link to a Suburban SF-35Q tune up kit and all of the parts.

    https://pdxrvwholesale.com/products/...5q-tune-up-kit
    Picking up a new limit switch tomorrow.

  5. #5
    Seasoned Camper
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    CA, UT, ID, WA until June 2023
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    If there isn't enough air flow across the High Limit Switch it will get too hot and it will do it's job - cycle off as the temp reaches 160 degrees. I would be looking at all of the outputs from the furnace and make sure that they aren't folded over on themselves or pinched. Is there heat coming out of all of the heater vents in the trailer with sufficient airflow. Nothing that I see in the service manual says what the outlet temperature SHOULD be - probably because the closer to the furnace you are with measuring the outlet air the hotter it will be.
    (Ordered 7/13/20) 2021 Solitude 310GK, FBP, DP, HP, Toppers, Solar, MORryde 7K IS w/Disc Brakes
    Built 9/9/20; To Paint 9/11/20 (5-6 weeks); Done Paint 10/1/20; MORryde axle upgrade 10/5/20; Done at MORryde and paid for 10/8/20; Arrived at Dealer 10/20/20; picked up 11/7/20

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