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2021 367BHS Suburban Model SFV-35Q Troubleshooting Help

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  • 2021 367BHS Suburban Model SFV-35Q Troubleshooting Help

    Hello! Our furnace stopped working the other day and I wonder if others have had the same experience. It would work occasionally but then shut off in the middle of the night. I should probably mention that the temps have been between 0 and 30 lately.

    When we up the temperature on the thermostat we hear the thermostat click but nothing happens with the furnace...no clicking, and the blower doesn't come on.

    Our propane is full, the stove works just fine.

    I had the batteries tested and replaced one that had 1/4 capacity left, but that didn't change anything.

    My thought is maybe the blower motor needs replacing, but I've also read that faulty wires, failed time delay relay or loose wiring could be the culprit. We just don't know where or how to start troubleshooting more.

    Any help is welcome, thank you!​

  • #2
    Originally posted by TheMcclearys View Post
    Hello! Our furnace stopped working the other day and I wonder if others have had the same experience. It would work occasionally but then shut off in the middle of the night. I should probably mention that the temps have been between 0 and 30 lately.

    When we up the temperature on the thermostat we hear the thermostat click but nothing happens with the furnace...no clicking, and the blower doesn't come on.

    Our propane is full, the stove works just fine.

    I had the batteries tested and replaced one that had 1/4 capacity left, but that didn't change anything.

    My thought is maybe the blower motor needs replacing, but I've also read that faulty wires, failed time delay relay or loose wiring could be the culprit. We just don't know where or how to start troubleshooting more.

    Any help is welcome, thank you!​
    There's a device called a "sail switch" that checks the status of the blower motor (if it's running). See https://gdrvowners.com/forum/operati...on-the-furnace

    Also see Furnace Troubleshooting here: https://gdrvowners.com/forum/operati...roubleshooting

    If there's specific questions after you check those resources, don't hesitate to ask for clarification.

    Howard
    Last edited by howson; 03-06-2024, 07:40 PM.
    Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

    2017 Ford F-350 DRW, '19 315RLTSPlus

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    • #3
      Originally posted by TheMcclearys View Post
      Here is a copy of the Service Manual and a parts list for these furnaces.
      Attached Files
      Pat and Karen
      2021 Solitude 310GK, Full Body Paint, Dual Pane Windows, Heat Pump, Slide Toppers, Solar, MORryde 7K IS w/Disc Brakes, Splendide W/D Stacked Pair

      Comment


      • #4
        Regarding furnace blower not running when the thermostat calls for heat:

        1. Assuming the furnace isn’t in an error state (lockout - clear by turning the furnace off and on), a likely cause is the sail switch is stuck closed. The first thing the control board does when the thermostat calls for heat is to check the status of the sail switch, if closed the control board immediately enters an error state, fan isn’t running so the sail switch shouldn’t be closed. Only after verifying the sail switch is open is the fan motor is started.

        2. If the fan runs for about 20 - 30 seconds and shuts down, the three most likely culprits are: sail switch not closing, high limit switch open (very very seldom), or on a Suburban the on/off switch has been turned off - left side under the exterior furnace cover.

        BTW - the on/off switches on Suburban and Dometic/Atwood furnaces are different in functionality. The Suburban switch opens the sail switch/limit switch circuit preventing the furnace from ever lighting - fan still runs. On a Dometic/Atwood furnaces the on/off switch shuts everything down and is also a circuit breaker. The most frequent cause of a tripped Dometic switch is overheating caused by blocked return air ducts or more frequently a ripped/lose/disconnected hot air duct causing the furnace to suck in just heated air rather than cold air.

        3. If the fan runs for three to five minutes before shutting down, the control board is going through three attempts to purge the combustion chamber and then ignite.

        Likely causes:

        a) out of propane
        b) bad control board
        c) bad igniter - extremely rare to fail.
        d) gas valve not opening. - extremely rare

        4. If the furnace lights for five to eight seconds then goes out the most likely cause is the control board. Could be the igniter which is also the flame detector, but highly unlikely.

        5. Really weird - part of a mud dauber nest rattling around near the igniter, sometimes blocking the spark.
        Colan Arnold
        2016 Momentum 397TH
        Full time since 2016

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        • #5
          Thank you all for the input! We think it’s the control board. We checked the sail switch and it’s working properly.

          Our issue now is we don’t know how to access the control board. It’s a vertical furnace so the board is located on top and in the back right corner. We can’t remove the case around it and couldn’t figure out how to get the unit out of the casing.

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          • #6
            Originally posted by TheMcclearys View Post
            Thank you all for the input! We think it’s the control board. We checked the sail switch and it’s working properly.

            Our issue now is we don’t know how to access the control board. It’s a vertical furnace so the board is located on top and in the back right corner. We can’t remove the case around it and couldn’t figure out how to get the unit out of the casing.
            As I read through the boards I'll copy something and put it into this Word file I have - some day I'll need it, I say. I just copied THIS the other day about vertical furnaces. Hopefully some part of this description will help with your project.

            "Removing a newer vertically mounted Suburban furnace is a pain.

            The horizontally mounted units have a screw at the back accessible after removing the plate holding the rear vent hoses. The vertical mounted unit has the same screw.

            At the front after removing the outer cover is another screw on both the vertical and horizontal units.

            NOW THE HARD PART - a vertical mounted unit is a slightly different model with more screws in the furnace from the outer case to the inner. Oftentimes these screws are located where it is impossible to access the screws. Ok, so remove the entire furnace, case and all after disconnecting all of the hoses- if it were only that easy. Furnace is held in place with a couple of 90 degree L brackets. If you can, remove the L brackets from the furnace. Sometimes it is really difficult to get at the screws on the L bracket into the furnace. Okay, (there is a catch) so just remove the other screws in the bracket leaving the brackets attached to the furnace. Next problem, trying to slide the unit out the hole with the L brackets still attached is difficult at best. Opening is too small!!!"​
            Pat and Karen
            2021 Solitude 310GK, Full Body Paint, Dual Pane Windows, Heat Pump, Slide Toppers, Solar, MORryde 7K IS w/Disc Brakes, Splendide W/D Stacked Pair

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            • #7
              pengle

              When pasting another members information you should give them the credit for the information or state their username incase someone has a question they will know who to direct it to.

              Brian
              Brian & Michelle
              2018 Reflection 29RS
              2022 Chevy 3500HD

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              • #8
                Originally posted by Country Campers View Post
                pengle

                When pasting another members information you should give them the credit for the information or state their username incase someone has a question they will know who to direct it to.

                Brian
                If I had copied that user name down I would have done that. I don't even remember if I got the information on this board or the "other" board or Facebook. I don't even HAVE a vertical furnace installation on MY rig, but I felt the details would help someone who does.
                Pat and Karen
                2021 Solitude 310GK, Full Body Paint, Dual Pane Windows, Heat Pump, Slide Toppers, Solar, MORryde 7K IS w/Disc Brakes, Splendide W/D Stacked Pair

                Comment


                • #9
                  I'm having the same problem. My furnace is the same model, but my RV is a 2022 303RLS. The sail switch is fine. Swapped it out and same issue. Bench tested good. But when it went back in the camper...it doesn't work. Does anyone know where the reset button is on the furnace?

                  Sadly, the longer I own this, the more regrets I (we) have.

                  I'm new to signing up for the forum, so I still need to work on my profile.
                  Diana & Darren with our two German Shepherd Dogs Jaz and Lzzy
                  We are Navy (me) and Army vets/retirees

                  2012 GMC 2500 SLT 4x4 extended cab, long wheel base
                  2022 Reflection 303 RLS​

                  Comment


                  • #10
                    Originally posted by RemyJL View Post
                    I'm having the same problem. My furnace is the same model, but my RV is a 2022 303RLS. The sail switch is fine. Swapped it out and same issue. Bench tested good. But when it went back in the camper...it doesn't work. Does anyone know where the reset button is on the furnace?

                    Sadly, the longer I own this, the more regrets I (we) have.

                    I'm new to signing up for the forum, so I still need to work on my profile.
                    Welcome to the forum.

                    Can you elaborate? What are the symptoms and what exactly (besides the sail switch) have you checked? Did you check out the troubleshooting thread referenced in post 2?

                    Howard
                    Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

                    2017 Ford F-350 DRW, '19 315RLTSPlus

                    Comment


                    • #11
                      RemyJL When you reinstall the unit, leave all the duct work off and run it. If it does not act up then you have a ducting issue. If you can test both the sail switch and the thermal switch during installed operation to determine which one may be giving you the issue.

                      One other thing to remember is to beech test the unit as close to install as possible. This means somehow using the same orientation and covers that are on the unit when it's in the camper. Something as simple as critter covers could if not fitted correctly affect airflow, just like the ducting can affect air flow.
                      Joseph
                      Tow
                      Vehicle: 2024 GMC K3500 Denali Ultimate Diesel
                      Coach: 303RLS Delivered March 5, 2021
                      South of Houston Texas

                      Comment


                      • #12
                        howson and Jlawles2 es2 the furnace just up and stopped working. Propane - good flow, at first when the thermostat was turned on you could hear a click, but not more. Troubleshooting said it had to be blown out yearly. Mobile mechanic said the usual culprit was a sail switch. Swapped it out...still nothing, even after blowing it out. Sent to the local RV shop, who bench tested. They said it tested good. I don't know which orientation they had the unit in while testing. We weren't allowed in the mechanics bay when they tested. Brought it home, installed and nothing... The duct work was not connected when it was put back in the bay and still didn't work. The hubby tried it after with the ducting installed. Fuses are all good.

                        I don't know where the thermal switch is located.

                        Still don't know if/where there is a reset switch/button.

                        BTW, what's the part called to the left of the sail switch that has a blue power relay sitting on a circuit board (not the one at the top)?

                        The link in post #2, the troubleshooting one is a dead link.
                        Diana & Darren with our two German Shepherd Dogs Jaz and Lzzy
                        We are Navy (me) and Army vets/retirees

                        2012 GMC 2500 SLT 4x4 extended cab, long wheel base
                        2022 Reflection 303 RLS​

                        Comment


                        • #13
                          Originally posted by RemyJL View Post
                          howson and Jlawles2 es2 the furnace just up and stopped working. Propane - good flow, at first when the thermostat was turned on you could hear a click, but not more. Troubleshooting said it had to be blown out yearly. Mobile mechanic said the usual culprit was a sail switch. Swapped it out...still nothing, even after blowing it out. Sent to the local RV shop, who bench tested. They said it tested good. I don't know which orientation they had the unit in while testing. We weren't allowed in the mechanics bay when they tested. Brought it home, installed and nothing... The duct work was not connected when it was put back in the bay and still didn't work. The hubby tried it after with the ducting installed. Fuses are all good.

                          I don't know where the thermal switch is located.

                          Still don't know if/where there is a reset switch/button.

                          BTW, what's the part called to the left of the sail switch that has a blue power relay sitting on a circuit board (not the one at the top)?

                          The link in post #2, the troubleshooting one is a dead link.
                          Link is fixed (sorry about that).

                          The only "reset switch" (that I know of) is cycling the thermostat OFF and then back to HEAT.

                          If the furnace worked fine outside of the RV but doesn't work when installed, then something external is likely the issue.

                          What would I check?

                          1) 12vDC where it should be at the furnace.
                          2) The 12vDC return (commonly called "ground") is connected to a known good source.
                          3) The thermostat wiring is good (continuity tests or verifying the 12vDC signal makes it to the control board when heat is called for).

                          Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

                          2017 Ford F-350 DRW, '19 315RLTSPlus

                          Comment

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