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  • Furnace won’t reach temp - intermittent

    2018 374th Solitude
    Suburban SF 35q furnace won’t cycle in colder temps (below 45). Furnace comes on runs for awhile and shuts off before reaching thermostat temp. If I turn off and back on, will run again it heats but will then do the same thing. Once outside temp increase, it will cycle as it should from the thermostat.

    Have had a tech out a couple of times, replaced board with dinosaur brand, high limit switch and thermostat. Still same issue. No blockages in the furnace. Sail switch tested good. Pretty sure the high limit switch is causing the shutdown. What could be causing the shutdown?

  • #2
    Originally posted by DougnDot View Post
    2018 374th Solitude
    Suburban SF 35q furnace won’t cycle in colder temps (below 45). Furnace comes on runs for awhile and shuts off before reaching thermostat temp. If I turn off and back on, will run again it heats but will then do the same thing. Once outside temp increase, it will cycle as it should from the thermostat.

    Have had a tech out a couple of times, replaced board with dinosaur brand, high limit switch and thermostat. Still same issue. No blockages in the furnace. Sail switch tested good. Pretty sure the high limit switch is causing the shutdown. What could be causing the shutdown?
    Welcome to the tech forum Doug and Dot! Before we get into the furnace issue, I wanted to provide you a link to help with future forum navigation:
    https://gdrvowners.com/forum/main-fo...to-new-members

    Now, on to the furnace. My first thought was that the limit switch might have failed. But the technician replaced it. In my opinion, this means that the limit switch is actually seeing high temperature and shutting down. I know you say that there are no blockages in the furnace. But if you can, I'd dive into this area a little more. I'd remove each outlet on the furnace and place a hair dryer in the vent. Seal up the hair dryer/vent with removeable tape and turn it on high. Then check the outlets registers to see if there is air flow. I've seen many occurrences where a vent tube get crushed during assembly and needs repair. Most, if not all vents will be installed in the underbelly, and you might need to peek in there to see what's going on.

    Jim
    GDRV Forum Moderator
    GDRV SW USA Rally Support Coordinator

    Jim and Ginnie
    2017 Reflection 297RSTS

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    • #3
      DougnDot Welcome to the family and the forum!
      Jerry and Kelly Powell, with Halo, Nash, Reid, Cleo, and the new baby kitty Rosie..
      Pilot (Zebulon), NC
      2020 Solitude 390RK-R

      Comment


      • #4
        I have the same problem in my 25G. The heat produced is excessive for the amount of airflow. And I suspect as you do that the furnace goes over-temp and locks it's self out. I can visually inspect 2 of the duct paths and they are open and clear. The under unit duct to the bedroom produces about the same volume of flow. I've spoken with customer support, was connected to a specialist who was stumped, sent me a ducting drawing at my request, and said she would contact a person involved in service for an opinion. She also said she wasn't aware that this was a common problem. Since I am 4 hours away from a warranty center she verbally authorized an independent shop to look at it. She promised to get back to me with the service guys opinion and an authorization for independent warranty coverage. That's well over a week ago I believe. No response yet. I think this will be a tough one to resolve because the only time the furnace will have to run long enough to trip the over temp cutout, is in very cold weather. It will be hard to duplicate now that it's warmer. Best of luck and please post if you find a resolution, as I will too.

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        • #5
          Doug n Dot, Did you find a resolution?

          Comment


          • #6
            Originally posted by DougnDot View Post
            2018 374th Solitude
            Suburban SF 35q furnace won’t cycle in colder temps (below 45). Furnace comes on runs for awhile and shuts off before reaching thermostat temp. If I turn off and back on, will run again it heats but will then do the same thing. Once outside temp increase, it will cycle as it should from the thermostat.

            Have had a tech out a couple of times, replaced board with dinosaur brand, high limit switch and thermostat. Still same issue. No blockages in the furnace. Sail switch tested good. Pretty sure the high limit switch is causing the shutdown. What could be causing the shutdown?
            We have a 2020 Solitude 310 exhibiting very similar symptoms. I have changed: 1. Logic board and replaced with a Dinosaur board
            2. Ignitor and made sure the new ignitor is properly aligned
            3. Sail switch
            4. Over temp switch
            5. Gas valve
            6. Gas regulator
            7. Thermostat

            I have verified that when the furnace shuts down, the thermostat is still calling for heat.

            Our furnace will hold the temp within its 2 degree range. It will not warm up the camper from 50F to 70F. It seems like the long run is the problem, and nobody has been able to diagnose root cause and fix the problem. I would love to know of someone has had their issue fixed.

            Last edited by Kings7248; 11-16-2022, 05:13 PM. Reason: Adding further detail
            2021 GMC Denali, CC, DRW, Duramax, 25K B&W Hitch
            2020 Solitude 310GK
            Previous: 2018 Reflection 337
            Previous: 2016 Imagine 2600RB

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            • #7
              Originally posted by Kings7248 View Post

              We have a 2020 Solitude 310 exhibiting very similar symptoms. I have changed: 1. Logic board and replaced with a Dinosaur board
              2. Ignitor and made sure the new ignitor is properly aligned
              3. Sail switch
              4. Over temp switch
              5. Gas valve
              6. Gas regulator
              7. Thermostat

              I have verified that when the furnace shuts down, the thermostat is still calling for heat.

              Our furnace will hold the temp within its 2 degree range. It will not warm up the camper from 50F to 70F. It seems like the long run is the problem, and nobody has been able to diagnose root cause and fix the problem. I would love to know of someone has had their issue fixed.
              What's really odd is the cold air return is through the pantry. I know this sounds crazy, but try running the furnace with the pantry door open. If that doesn't help, direct a fan blowing into the pantry. If my guess is correct, the problem is the lack of sufficient return air which leads to overheating in the furnace.

              Please let me know if you try one or both of these ideas and what is the result. Specifics (outside temp, inside temp and thermostat settings) will help!

              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


              • #8
                Kings7248
                I've tried a number of times to write this post because I want to be precise and direct. The furnace only requires 55 square inches of return air area for the furnace to have "enough" air to operate. The 3 gaping holes in the 310GK (pantry, hutch, stairs) are more than enough. But the furnace isn't ducted to those openings, so basically the entire passthrough area is the cold air return for our furnace. So if it is getting enough air what else could cause the high limit to get too hot. The heater box is cooled by the ambient air moving through the heater box. Less air moving means the box gets hotter until the limit switch opens and stops the gas.
                I'm a former furnace/appliance tech. Here is how I would tackle this. Does the outlet air (hot) continue to rise at one of the registers until the high limit shuts off. Find the register that is the closest to the furnace. ​You'll need an infrared thermometer. They are handy for a lot of things. I was able to see 140* at one of my registers tonight. You can use that as a baseline. Outside temp was 38*. Inside temp was 71*.
                IF the high limit switch is easy to get at then I would remove the two leads and connect the two leads together (yes, tape them up) and run the temp test again. If your reading is 5-10* higher than before I would shut the furnace down before you get things too hot.
                On another forum someone suggested disconnecting the individual ducts from the furnace and blowing air from a hair dryer down them to make sure they aren't kinked or plugged.
                Power to the control board (for controlling if the gas is on or off) comes through the thermostat, then the valve switch, then the high limit, then the sail switch.
                You've already replaced everything in that circuit, so the ducting is where I would look next.
                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
                  Originally posted by pengle View Post
                  Kings7248
                  I've tried a number of times to write this post because I want to be precise and direct. The furnace only requires 55 square inches of return air area for the furnace to have "enough" air to operate. The 3 gaping holes in the 310GK (pantry, hutch, stairs) are more than enough. But the furnace isn't ducted to those openings, so basically the entire passthrough area is the cold air return for our furnace. So if it is getting enough air what else could cause the high limit to get too hot. The heater box is cooled by the ambient air moving through the heater box. Less air moving means the box gets hotter until the limit switch opens and stops the gas.
                  I'm a former furnace/appliance tech. Here is how I would tackle this. Does the outlet air (hot) continue to rise at one of the registers until the high limit shuts off. Find the register that is the closest to the furnace. ​You'll need an infrared thermometer. They are handy for a lot of things. I was able to see 140* at one of my registers tonight. You can use that as a baseline. Outside temp was 38*. Inside temp was 71*.
                  IF the high limit switch is easy to get at then I would remove the two leads and connect the two leads together (yes, tape them up) and run the temp test again. If your reading is 5-10* higher than before I would shut the furnace down before you get things too hot.
                  On another forum someone suggested disconnecting the individual ducts from the furnace and blowing air from a hair dryer down them to make sure they aren't kinked or plugged.
                  Power to the control board (for controlling if the gas is on or off) comes through the thermostat, then the valve switch, then the high limit, then the sail switch.
                  You've already replaced everything in that circuit, so the ducting is where I would look next.
                  pengle
                  Good morning. I did a little different take on your recommendation to check the duct work. I pulled the furnace, shorted the high limit switch, and I put a couple of leads on the high limit switch so I could put my ohm meter across it and see if the high limit switch ever tripped. Temps were: outside, 33F, camper temp 48F, thermostat set to 70F

                  To shorten the story, the furnace quit, the high limit switch did not open, and I discovered that my new regulator was not auto switching to the full propane tank and the regulator was no closing the port on the empty tank side of the regulator. I put a Camco heavy duty regulator in, and was able to warm the camper up from 50F to 70F, without issue. This is the first time this camping season this has worked. I have now put the high limit switch back into the circuit and will run the warm up test again to see if the problem is really fixed. Thank you for your insight and help.
                  2021 GMC Denali, CC, DRW, Duramax, 25K B&W Hitch
                  2020 Solitude 310GK
                  Previous: 2018 Reflection 337
                  Previous: 2016 Imagine 2600RB

                  Comment


                  • #10
                    Originally posted by Kings7248 View Post

                    pengle
                    Good morning. I did a little different take on your recommendation to check the duct work. I pulled the furnace, shorted the high limit switch, and I put a couple of leads on the high limit switch so I could put my ohm meter across it and see if the high limit switch ever tripped. Temps were: outside, 33F, camper temp 48F, thermostat set to 70F

                    To shorten the story, the furnace quit, the high limit switch did not open, and I discovered that my new regulator was not auto switching to the full propane tank and the regulator was no closing the port on the empty tank side of the regulator. I put a Camco heavy duty regulator in, and was able to warm the camper up from 50F to 70F, without issue. This is the first time this camping season this has worked. I have now put the high limit switch back into the circuit and will run the warm up test again to see if the problem is really fixed. Thank you for your insight and help.
                    Sorry, I forgot to attach a picture. Here is the picture:
                    Attached Files
                    2021 GMC Denali, CC, DRW, Duramax, 25K B&W Hitch
                    2020 Solitude 310GK
                    Previous: 2018 Reflection 337
                    Previous: 2016 Imagine 2600RB

                    Comment


                    • #11
                      pengle I'm surprised you saw 140*...wouldn't you consider that pretty darn hot for a register?
                      2018 Dodge 3500 6.7 Cummins w Aisin and 9 cup holders
                      2021 Reflection 303RLS, Haloview RD7, Strong-arms, Micro-Air364
                      .........It's weird being the same age as old people.....

                      Comment


                      • #12
                        Originally posted by Scott'n'Wendy View Post
                        pengle I'm surprised you saw 140*...wouldn't you consider that pretty darn hot for a register?
                        That IS at the high end of the scale The manufacturer says that the outlet register temp can be 40* - 70* above the ambient temp. So if it is 70* inside your trailer then 140* would be OK. The high limit thermostat on the furnace is around 160*, so it isn't getting any hotter than that in a properly operating RV furnace.
                        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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