Announcement

Collapse
No announcement yet.

Hopefully Resolved!! Furnace Fan Turned on Spontaneously?

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Hopefully Resolved!! Furnace Fan Turned on Spontaneously?

    Thermostat was set to off. Turned on the electric switch in the control center for hot water heater, and instantly the furnace fan started up. Cycled through the thermo to get back to Off, still ran. Cycled through again and it finally shut off. Any ideas of why this happened or how to prevent it in the future?

    Or was this an April Fool's Day joke one of you pulled on us?

    Andi
    Andi
    Brookings SD
    2018 Reflection 337RLS
    2019 GMC Sierra 3500HD Duramax

  • #2
    No suggestions? It happened again tonight. (Were gone all day so not sure if it did it prior to this.)

    Stat heat temp set to 62 but Off. Temp in RV showing 74. Don't think we turned anything else on when it happened this time. (Hubby was in shower, I was outside and came back in to it running.)

    Had to cycle through twice again for it to shut off. Then about 5 min. later it started up again. Pulled the fuse and will leave it out unless we absolutely need to run furnace.
    Andi
    Brookings SD
    2018 Reflection 337RLS
    2019 GMC Sierra 3500HD Duramax

    Comment


    • #3
      Originally posted by Andi View Post
      No suggestions? It happened again tonight. (Were gone all day so not sure if it did it prior to this.)

      Stat heat temp set to 62 but Off. Temp in RV showing 74. Don't think we turned anything else on when it happened this time. (Hubby was in shower, I was outside and came back in to it running.)

      Had to cycle through twice again for it to shut off. Then about 5 min. later it started up again. Pulled the fuse and will leave it out unless we absolutely need to run furnace.
      Give me a second to look at the schematic for the heater--be right back.
      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


      • #4
        From GD's website, I think you have a Suburban Furnace 2470A (SFV-35Q) in your 337. The info below is from the Suburban RV Furnaces Service & Training Manual. (I can only find a copy on the heartland owners website! Google it and you'll find it.)

        The wall thermostat controls the operation of the furnace by reacting to room temperature. This allows current to flow through the ON/OFF switch to the module board. The module board constantly checks for a minimum 9.5 volts. If there is not 9.5 volts, the module board will go into a stand by mode until adequate power is supplied. It will then resume
        normal operation. Upon a call from the thermostat, the module board thermostat circuit will go active. The sail switch circuit is verified as being open. The blower output is energized. Blower motor starts.


        Click image for larger version

Name:	htr circuit.JPG
Views:	1155
Size:	144.2 KB
ID:	15908

        So what all of this tells me is that when you turn on the water heater switch (which passes +12v across it when turned on) that the output wire from the heater switch and the wire from the module board to the water heater (BLO > R on the motor) are shorted together. It might even be sooner or on the thermostat line, assuming the sail switch is operational.

        This will take some investigation with an ohm meter to track down. It could be a staple that has finally worked it's way through the insulation of the wiring, or any number of other possibilities. Should be relatively simple, though, as the furnace is in the hutch (your 337 is very similar to my 315). I *assume* the water heater switch and light panel are at the end of the hutch at eye level--just like my 315.

        Let me see if I can find some pictures of this area...





        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


        • #5
          I think these are the red and blue (thermostat and +12v) coming in to the module board. (On the schematic they come in the bottom left, then work around to the module board top right.) My guess is the blue wire is somehow getting power when the water heater switch is turned on (so it's the output side of the switch), thus somewhere between the module board and the water heater switch there's something pinched or chaffed which is causing a short.

          I probably didn't help one bit, did I? Sorry--I can't think of a simple way to troubleshoot this other than removing 12V power and breaking out the 'ol ohmmeter. :(

          Click image for larger version  Name:	blue red.JPG Views:	0 Size:	129.9 KB ID:	15912
          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


          • #6
            Andi
            Hi Andi

            I missed your question earlier . . .
            The furnace and the water heater are side-by-side. The wiring is draped across both and I would guess that the water heater power and furnace fan power wires have melted together where they cross over the furnace.

            Rob
            Cate & Rob
            (with Border Collies Molly & Angel + Kitties Hazel & Elsie)
            2015 Reflection 303RLS
            2022 F350 Diesel CC SB SRW Lariat
            Bayham, Ontario, Canada

            Comment


            • #7
              Originally posted by howson View Post
              From GD's website, I think you have a Suburban Furnace 2470A (SFV-35Q) in your 337. The info below is from the Suburban RV Furnaces Service & Training Manual. (I can only find a copy on the heartland owners website! Google it and you'll find it.)

              This will take some investigation with an ohm meter to track down. It could be a staple that has finally worked it's way through the insulation of the wiring, or any number of other possibilities. Should be relatively simple, though, as the furnace is in the hutch (your 337 is very similar to my 315). I *assume* the water heater switch and light panel are at the end of the hutch at eye level--just like my 315.

              Let me see if I can find some pictures of this area...


              Thanks, howson . Our hutch has 3 drawers in the center, Rudy thinks the furnace has to be accessed through the basement (after unloading everything and taking the panel off ), so we were waiting for daylight to take a look.

              ​​​​​​​Thanks for your reply too, Cate&Rob. Knowing that, we decided we probably shouldn't run the furnace or water heater on electric until he can look at the wiring. Unfortunately it got down to 32F this morning and 52 in the RV - glad we have the fireplace and a small space heater!
              Andi
              Brookings SD
              2018 Reflection 337RLS
              2019 GMC Sierra 3500HD Duramax

              Comment


              • #8
                Andi,
                Hi Andi (&Rudy)

                You are correct that the furnace is accessed by removing the rear wall panel in the pass thru storage area. But . . . you might be able to see it and the water heater, plus the 12V wiring from the main panel, by removing the drawers in hutch. Good luck . . . hopefully the problem is obvious when you get the area opened up.

                Rob
                Cate & Rob
                (with Border Collies Molly & Angel + Kitties Hazel & Elsie)
                2015 Reflection 303RLS
                2022 F350 Diesel CC SB SRW Lariat
                Bayham, Ontario, Canada

                Comment


                • #9
                  Originally posted by Cate&Rob View Post
                  Andi,
                  Hi Andi (&Rudy)

                  You are correct that the furnace is accessed by removing the rear wall panel in the pass thru storage area. But . . . you might be able to see it and the water heater, plus the 12V wiring from the main panel, by removing the drawers in hutch. Good luck . . . hopefully the problem is obvious when you get the area opened up.

                  Rob
                  You're right, Cate&Rob we can see some of it by removing the drawers, but unfortunately not a good enough view to know what's wrong. Put in a call to GD and they started a case for us, also have a mobile tech coming out this afternoon. Hopefully the rain will stop by then so all the stuff in the basement doesn't get wet.

                  Only supposed to have a high today of 43F - might have to go sit in the pickup with the seat heater on to get warmed up!
                  Andi
                  Brookings SD
                  2018 Reflection 337RLS
                  2019 GMC Sierra 3500HD Duramax

                  Comment


                  • #10
                    howsfran Cate&Rob , if there was a short or melted wire, wouldn't it blow a fuse? We had a mobile tech here and that's what he said. Of course now that he's here, we can't re-create the problem , just like when you take your car to the mechanic and it won't make the noise. ​​​​​​​
                    Andi
                    Brookings SD
                    2018 Reflection 337RLS
                    2019 GMC Sierra 3500HD Duramax

                    Comment


                    • #11
                      Originally posted by Andi View Post
                      howsfran Cate&Rob , if there was a short or melted wire, wouldn't it blow a fuse? We had a mobile tech here and that's what he said. Of course now that he's here, we can't re-create the problem , just like when you take your car to the mechanic and it won't make the noise.
                      Only if the power wire was shorted to ground. In this case the theory is a +12v wire is shorting to another +12v wire, thus a device (your heater) is powering on inadvertently when power is provided. The heater's fan doesn't care where the power comes from--if it has 12v across it the fan will happily run all day.

                      There's a wire that's chaffed, or as Rob mentioned, melted, somewhere between the water heater switch and the heater. I promise if you inspect those wires you'll find the problem. There will be physical damage to the insulation of the wires. Most likely where they are tied or secured to something (like a stud).

                      Funny you tagged my DW. Get it? "hows" "fran"?
                      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
                        Andi ,
                        I hope this makes it easier to visualize. The first diagram is an over-simplified view of how the water heater and furnace *should* work. Water heater turns on when the 12v switch is turned on and the furnace turns on when the thermostat applies power.

                        Click image for larger version  Name:	Circuit 1.JPG Views:	5 Size:	27.2 KB ID:	15991

                        Now a gremlin gets in the circuit and adds a path for power to cross to the furnace after the water heater switch. The furnace now thinks the thermostat has applied power--it has no idea the gremlin did it!

                        Click image for larger version  Name:	Circuit 2.JPG Views:	4 Size:	31.7 KB ID:	15992

                        The term is the same, "short", but there's no direct path back to the battery so the fuse (not shown in diagram) doesn't blow.

                        Hope that helps...

                        -Howard
                        Last edited by howson; 04-03-2020, 08:31 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

                        Comment


                        • #13
                          Originally posted by howson View Post

                          Only if the power wire was shorted to ground. In this case the theory is a +12v wire is shorting to another +12v wire, thus a device (your heater) is powering on inadvertently when power is provided. The heater's fan doesn't care where the power comes from--if it has 12v across it the fan will happily run all day.

                          There's a wire that's chaffed, or as Rob mentioned, melted, somewhere between the water heater switch and the heater. I promise if you inspect those wires you'll find the problem. There will be physical damage to the insulation of the wires. Most likely where they are tied or secured to something (like a stud).

                          Funny you tagged my DW. Get it? "hows" "fran"?
                          Okay, makes sense.

                          Guess I hit the first '@how' that popped up. So how is Fran?
                          Andi
                          Brookings SD
                          2018 Reflection 337RLS
                          2019 GMC Sierra 3500HD Duramax

                          Comment


                          • #14
                            Originally posted by howson View Post
                            Andi ,
                            I hope this makes it easier to visualize. The first diagram is an over-simplified view of how the water heater and furnace *should* work. Water heater turns on when the 12v switch is turned on and the furnace turns on when the thermostat applies power.

                            Click image for larger version Name:	Circuit 1.JPG Views:	5 Size:	27.2 KB ID:	15991

                            Now a gremlin gets in the circuit and adds a path for power to cross to the furnace after the water heater switch. The furnace now thinks the thermostat has applied power--it has no idea the gremlin did it!

                            Click image for larger version Name:	Circuit 2.JPG Views:	4 Size:	31.7 KB ID:	15992

                            The term is the same, "short", but there's no direct path back to the battery so the fuse (not shown in diagram) doesn't blow.

                            Hope that helps...

                            -Howard
                            Love the gremlin illustration , thanks for the visual. Now I know who/what to look for - wonder if a mouse trap would work on the little guy?
                            Andi
                            Brookings SD
                            2018 Reflection 337RLS
                            2019 GMC Sierra 3500HD Duramax

                            Comment


                            • #15
                              Andi -- was this resolved? Just curious...hope all is well!
                              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

                              Working...
                              X