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  • Furnace Troubleshooting

    Having never delved into the deep-dark secrets contained within the shiny metal case of the device called "The Heater", recent threads here on the forum have led me to learning more about this mysterious appliance.

    I found the video below very informative. What did not surprise me is the #1 problem is voltage.




    Last edited by howson; 02-24-2023, 06:28 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

  • #2
    Thanks Howard. That is a very informative video.

    Jim
    Jim and Ginnie
    2024 Solitude 310GK
    GDRV Technical Forum Moderator
    GDRV Rally Support Coordinator

    Comment


    • #3
      Originally posted by howson View Post
      Having never delved into the deep-dark secrets contained within the shiny metal case of the device called "The Heater", recent threads here on the forum have led me to learning more about this mysterious appliance.

      I found the video below very informative. What did not surprise me is the #1 problem is voltage.


      We're on the road in upstate Minnesota. Got down to 40 last night, so we (tried) to turn the furnace on. Nothing. Verified we have plenty of LP gas and batteries are good.

      We have a Surburban Airxcel furnace that's controlled by switching the thermostat to "Heat Gas" mode and setting the desired temp above room temp. Per the video, we should hear the furnace fan come on immediately -- but we get nothing. No fan, no furnace ignition.

      I pulled the furnace cover panel from the outside hoping to find a loose electrical plug. Nothing there except an on-off override switch that I confirmed was on.

      I went into the basement to try to find wiring on the backside, but nothing was accessible. Looks like you have to remove the duct-work and pull the furnace to get to anything.

      I did verify the fuse in the distribution panel was good, and I even looked behind the monitor/control panel to make sure there wasn't a hidden furnace fuse. Nothing but the 2-amp awning light fuse.

      I'm guessing the furnace control panel is bad. Any other ideas?

      -Steve

      2018 Solitude 310GK, disc brakes
      Morryde SRE4000/XFactor with heavy duty shackles, V-Brackets in spring hangers
      2012 Ram 3500 SRW 6.7 Diesel, air bags
      18k B&W Companion, non-slider
      640 watts solar, 400 amp-hour Lion Safari UT 1300 battery bank
      Aims 1500 watt inverter/charger with ATS
      Somerset, WI

      Comment


      • #4
        Originally posted by steve&renee View Post

        We're on the road in upstate Minnesota. Got down to 40 last night, so we (tried) to turn the furnace on. Nothing. Verified we have plenty of LP gas and batteries are good.

        We have a Surburban Airxcel furnace that's controlled by switching the thermostat to "Heat Gas" mode and setting the desired temp above room temp. Per the video, we should hear the furnace fan come on immediately -- but we get nothing. No fan, no furnace ignition.

        I pulled the furnace cover panel from the outside hoping to find a loose electrical plug. Nothing there except an on-off override switch that I confirmed was on.

        I went into the basement to try to find wiring on the backside, but nothing was accessible. Looks like you have to remove the duct-work and pull the furnace to get to anything.

        I did verify the fuse in the distribution panel was good, and I even looked behind the monitor/control panel to make sure there wasn't a hidden furnace fuse. Nothing but the 2-amp awning light fuse.

        I'm guessing the furnace control panel is bad. Any other ideas?

        -Steve
        If the blower does not come on at all it could be a couple of things, but the board could certainly be one. The Dinosaur brand replacement comes with some diagnostic lights to help troubleshoot problems, but the stock board has none of these. It could be worth pulling your thermostat off the wall and making sure the furnace wires have not come loose. Failing that if you can get to where the connections are you can check that it’s getting the signal from the thermostat with a meter, and make sure it’s feeling 12v.
        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.​

        Neil Citro
        2018 Reflection 28BH Pepwave
        2019 F350 6.7L Long Bed Crew Cab

        Comment


        • #5
          Originally posted by ncitro View Post

          It could be worth pulling your thermostat off the wall and making sure the furnace wires have not come loose. Failing that if you can get to where the connections are you can check that it’s getting the signal from the thermostat with a meter, and make sure it’s feeling 12v.
          Thanks for the suggestion about the thermostat check. I gave that a try. Opened the thermostat cover and found a small circuit board with all wires attached. There was also a tiny fuse on the board. It was in good shape.

          After I got the thermostat back together, I retried the furnace. Still not working. But then I thought to try the AC since we just got hooked up to 30 amp service. That worked fine. So I tried the heat pump, when is supposed to operate when you switch the thermostat mode to "Heat Gas/Electric". Well the heat pump didn't start up either. Ambient temp is 80+, but I had the thermostat cranked up to 90+. Still no heat pump. Maybe the issue is a bad thermostat?

          Also, does anyone know how to get access to the control board. I didn't see it from the outside access or when I examined the furnace from inside the basement.
          Last edited by steve&renee; 06-21-2020, 04:00 PM. Reason: Added new investigative results with questions.
          2018 Solitude 310GK, disc brakes
          Morryde SRE4000/XFactor with heavy duty shackles, V-Brackets in spring hangers
          2012 Ram 3500 SRW 6.7 Diesel, air bags
          18k B&W Companion, non-slider
          640 watts solar, 400 amp-hour Lion Safari UT 1300 battery bank
          Aims 1500 watt inverter/charger with ATS
          Somerset, WI

          Comment


          • #6
            Originally posted by steve&renee View Post
            Also, does anyone know how to get access to the control board. I didn't see it from the outside access or when I examined the furnace from inside the basement.
            From the videos I saw it looks to be at the end of the fan assembly tucked in behind the outside switch.
            Dinosaur Electronics Universal Ignitor Board Model UIB S for Suburban Furnace https://www.youtube.com/watch?v=1Isx3JULT0Y
            https://www.loveyourrv.com/wp-conten...ace-Manual.pdf
            Suburban SF-30F furnace https://www.youtube.com/watch?v=foPtSXWNrXc
            Suburban SF-30 Time Delay Relay https://www.youtube.com/watch?v=cOKe1DaxrLQ
            Suburban SF-42 furnace https://www.youtube.com/watch?v=z14rCeJescQ
            Gene and Kim
            2015 Grand Design Reflection 317RST
            2017 RAM 3500 CC, LB, 4x2, 6.7L CTD

            Comment


            • #7
              Originally posted by steve&renee View Post

              So I tried the heat pump, when is supposed to operate when you switch the thermostat mode to "Heat Gas/Electric". Well the heat pump didn't start up either. Ambient temp is 80+, but I had the thermostat cranked up to 90+. Still no heat pump. Maybe the issue is a bad thermostat?
              Tried the heat pump tonight when temps were down quite a bit. Setting the thermostat mode to "Heat Gas/Electric" *does* start the heat pump. So now I'm back to suspecting the furnace control board. Thermostat seems to be working -- at least for Cooling and Heat Pump.

              It's cool out tonight, but with 30 amp service, the fireplace, and the heat pump, we'll be cozy. It's just my (growing) frustration with the reality of the non-functionality in these RV campers that's keeping me up at night. As the saying goes, I'm not a happy camper.

              -Steve

              2018 Solitude 310GK, disc brakes
              Morryde SRE4000/XFactor with heavy duty shackles, V-Brackets in spring hangers
              2012 Ram 3500 SRW 6.7 Diesel, air bags
              18k B&W Companion, non-slider
              640 watts solar, 400 amp-hour Lion Safari UT 1300 battery bank
              Aims 1500 watt inverter/charger with ATS
              Somerset, WI

              Comment


              • #8
                Originally posted by gbkims View Post

                From the videos I saw it looks to be at the end of the fan assembly tucked in behind the outside switch.
                Dinosaur Electronics Universal Ignitor Board Model UIB S for Suburban Furnace https://www.youtube.com/watch?v=1Isx3JULT0Y
                Thanks for the links, Gene. My model number is SF-35Q. I didn't find any videos specific to removing my model, and the weaving of the duct-work attached to the furnace with the plumbing lines looks a little daunting for me to tackle. (I'm assuming you have to detach the duct-work to remove the furnace.)

                I decided to drop the unit at the dealer next week. They said if I leave the unit with them, they'll try to work me in.

                -Steve
                2018 Solitude 310GK, disc brakes
                Morryde SRE4000/XFactor with heavy duty shackles, V-Brackets in spring hangers
                2012 Ram 3500 SRW 6.7 Diesel, air bags
                18k B&W Companion, non-slider
                640 watts solar, 400 amp-hour Lion Safari UT 1300 battery bank
                Aims 1500 watt inverter/charger with ATS
                Somerset, WI

                Comment


                • #9
                  Originally posted by steve&renee View Post

                  Thanks for the links, Gene. My model number is SF-35Q. I didn't find any videos specific to removing my model, and the weaving of the duct-work attached to the furnace with the plumbing lines looks a little daunting for me to tackle. (I'm assuming you have to detach the duct-work to remove the furnace.)

                  I decided to drop the unit at the dealer next week. They said if I leave the unit with them, they'll try to work me in.

                  -Steve
                  Good plan Steve,
                  Found a photo of SF-35Q and the circuit board looks even further back than the SF-30.
                  First thing I noticed in those videos was the furnace being pulled from the case to work on them.

                  Gene and Kim
                  2015 Grand Design Reflection 317RST
                  2017 RAM 3500 CC, LB, 4x2, 6.7L CTD

                  Comment


                  • #10
                    Originally posted by steve&renee View Post

                    Tried the heat pump tonight when temps were down quite a bit. Setting the thermostat mode to "Heat Gas/Electric" *does* start the heat pump. So now I'm back to suspecting the furnace control board. Thermostat seems to be working -- at least for Cooling and Heat Pump.

                    It's cool out tonight, but with 30 amp service, the fireplace, and the heat pump, we'll be cozy. It's just my (growing) frustration with the reality of the non-functionality in these RV campers that's keeping me up at night. As the saying goes, I'm not a happy camper.

                    -Steve
                    I am so confused. I was messing with the thermostat yesterday and inadvertently left the mode setting on "Heat Gas" with the temp cranked way up. Heat was not working.

                    Today, I was working on another project and happened to walk past the outside furnace access panel. The furnace was blasting hot air. Walked inside, and sure enough, the thermostat is on "Heat Gas", the furnace is running, and pumping hot air out of all ducts.

                    Shut it all down, waited a while, and tried the "Heat Gas" mode again. Works great. Switched back to AC 'cause it's really hot today.

                    Finished my other project and 6 hours after the last try, tried "Heat Gas" again. Works great!

                    So what's the diagnosis here? This past weekend while we were camping, we had no heat. Nothing else changed (except movement traveling on the way home), and now we have heat. Do I have an intermittent control board problem? Should I go ahead and replace the control board, or is there a way to rule it out?

                    (If I do replace the control board, I plan to go with the Dinosaur after-market board.)

                    -Steve
                    2018 Solitude 310GK, disc brakes
                    Morryde SRE4000/XFactor with heavy duty shackles, V-Brackets in spring hangers
                    2012 Ram 3500 SRW 6.7 Diesel, air bags
                    18k B&W Companion, non-slider
                    640 watts solar, 400 amp-hour Lion Safari UT 1300 battery bank
                    Aims 1500 watt inverter/charger with ATS
                    Somerset, WI

                    Comment


                    • #11
                      Originally posted by steve&renee View Post
                      Do I have an intermittent...
                      Yes. (Sorry...couldn't resist.)

                      From your original post: We have a Surburban Airxcel furnace that's controlled by switching the thermostat to "Heat Gas" mode and setting the desired temp above room temp. Per the video, we should hear the furnace fan come on immediately -- but we get nothing. No fan, no furnace ignition.

                      From the Suburban manual:
                      Click image for larger version  Name:	manual.JPG Views:	0 Size:	48.5 KB ID:	22629

                      I suspect the sail switch was stuck closed (much more common problem) and has since reopened. If the sail switch was closed (stuck), the fan will not start.

                      Find that sail switch so you know exactly where it's at. The next time the furnace won't start look at the sail switch to see it's position (or give the furnace a sharp slap on the side of the case).

                      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


                      • #12
                        Originally posted by howson View Post

                        Yes. (Sorry...couldn't resist.)

                        From your original post: We have a Surburban Airxcel furnace that's controlled by switching the thermostat to "Heat Gas" mode and setting the desired temp above room temp. Per the video, we should hear the furnace fan come on immediately -- but we get nothing. No fan, no furnace ignition.

                        From the Suburban manual:
                        Click image for larger version Name:	manual.JPG Views:	0 Size:	48.5 KB ID:	22629

                        I suspect the sail switch was stuck closed (much more common problem) and has since reopened. If the sail switch was closed (stuck), the fan will not start.

                        Find that sail switch so you know exactly where it's at. The next time the furnace won't start look at the sail switch to see it's position (or give the furnace a sharp slap on the side of the case).

                        Howard
                        OK. I can buy a stuck-closed sail switch. Especially with "The sail switch circuit is verified as being open" before "The blower output is energized. Blower motor starts."

                        My problem is locating (and possibly replacing) the sail switch. All my research so far says I need to pull the furnace to access the switch and circuit board. I'm really hesitant to tackle that without video guidance.

                        My thinking at this juncture is to take the rig to the dealer and tell them to replace the sail-switch and trouble-shoot the board. Looking for advice.

                        -Steve
                        2018 Solitude 310GK, disc brakes
                        Morryde SRE4000/XFactor with heavy duty shackles, V-Brackets in spring hangers
                        2012 Ram 3500 SRW 6.7 Diesel, air bags
                        18k B&W Companion, non-slider
                        640 watts solar, 400 amp-hour Lion Safari UT 1300 battery bank
                        Aims 1500 watt inverter/charger with ATS
                        Somerset, WI

                        Comment


                        • #13
                          Steve

                          The sail switch should be accessible by removing the outside cover, but I have seen a few less accessible. By having an intermittent problem you may just have loose wiring.

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

                          Comment


                          • #14
                            Steve,

                            I see the Suburban's seem to have newer SF-35Q versions where the sail switch is under the front plastic fan housing instead of being mounted externally.
                            Like:
                            Click image for larger version

Name:	SF-35Q Sail Switch under Fan Housing.jpg
Views:	3359
Size:	38.9 KB
ID:	22658

                            Last edited by gbkims; 06-26-2020, 10:19 AM.
                            Gene and Kim
                            2015 Grand Design Reflection 317RST
                            2017 RAM 3500 CC, LB, 4x2, 6.7L CTD

                            Comment


                            • #15
                              Originally posted by gbkims View Post
                              Steve,

                              I see the Suburban's seem to have newer SF-35Q versions where the sail switch is under the front plastic fan housing instead of being mounted externally.
                              Like:
                              Click image for larger version

Name:	SF-35Q Sail Switch under Fan Housing.jpg
Views:	3359
Size:	38.9 KB
ID:	22658
                              So I'm a little unclear. Does that mean the sail switch is not accessible unless you remove the unit, then remove the fan housing?
                              2018 Solitude 310GK, disc brakes
                              Morryde SRE4000/XFactor with heavy duty shackles, V-Brackets in spring hangers
                              2012 Ram 3500 SRW 6.7 Diesel, air bags
                              18k B&W Companion, non-slider
                              640 watts solar, 400 amp-hour Lion Safari UT 1300 battery bank
                              Aims 1500 watt inverter/charger with ATS
                              Somerset, WI

                              Comment

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