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Fridge overcooling

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  • red2dog45
    If the thermocouple fails in an Rv fridge will it signal the thermostat to go too high or too low?
    Message 1 of 10 , Jan 29
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      If the thermocouple fails in an Rv fridge will it signal the thermostat to go too high or too low?
    • Todd Barnard
      There is a thermistor in some models that will do that...What make and model is it? Email me directly if you want more info twbarnard@gmail.com
      Message 2 of 10 , Jan 29
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        There is a thermistor in some models that will do that...What make and model is it?

        Email me directly if you want more info
        twbarnard@...




        On Wed, Jan 29, 2014 at 7:45 PM, <red2dog45@...> wrote:
         

        If the thermocouple fails in an Rv fridge will it signal the thermostat to go too high or too low?


      • Akiva Panelas
        The thermocoupler does not do either. Its purpose is to signal that the pilot light is working so when the thermostat says more cold the regulator will open up
        Message 3 of 10 , Jan 29
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          The thermocoupler does not do either. Its purpose is to signal that the pilot light is working so when the thermostat says more cold the regulator will open up and allow more gas to pass through. It is a safety device so gas can not pass through the regulator with out blowing up.

          On Jan 29, 2014 9:45 PM, <red2dog45@...> wrote:
           

          If the thermocouple fails in an Rv fridge will it signal the thermostat to go too high or too low?

        • red2dog45
          My mistake in terminology. What I was referring to is the capillary tube that senses the evaporator temperature, and is connected to the thermostat. There is
          Message 4 of 10 , Jan 29
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            My mistake in terminology. What I was referring to is the capillary tube that senses the evaporator temperature, and is connected to the thermostat. There is one for both gas and electric in Dometic refrigerators.  What happens if that component fails?



            ---In classicrv@yahoogroups.com, <akivaca@...> wrote:

            The thermocoupler does not do either. Its purpose is to signal that the pilot light is working so when the thermostat says more cold the regulator will open up and allow more gas to pass through. It is a safety device so gas can not pass through the regulator with out blowing up.

            On Jan 29, 2014 9:45 PM, <red2dog45@...> wrote:
             

            If the thermocouple fails in an Rv fridge will it signal the thermostat to go too high or too low?

          • Todd Barnard
            That can give you a fluctuation in temps, but they tend to either work or not...does this happen on gas only?
            Message 5 of 10 , Jan 29
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              That can give you a fluctuation in temps, but they tend to either work or not...does this happen on gas only?
               


              On Wed, Jan 29, 2014 at 11:50 PM, <red2dog45@...> wrote:
               

              My mistake in terminology. What I was referring to is the capillary tube that senses the evaporator temperature, and is connected to the thermostat. There is one for both gas and electric in Dometic refrigerators.  What happens if that component fails?



              ---In classicrv@yahoogroups.com, <akivaca@...> wrote:

              The thermocoupler does not do either. Its purpose is to signal that the pilot light is working so when the thermostat says more cold the regulator will open up and allow more gas to pass through. It is a safety device so gas can not pass through the regulator with out blowing up.

              On Jan 29, 2014 9:45 PM, <red2dog45@...> wrote:
               

              If the thermocouple fails in an Rv fridge will it signal the thermostat to go too high or too low?


            • red2dog45
              I believe it is in gas use only. Still, what happens if the capillary tube fails? My Dometic manual also lists loss of a gas charge in the thermostat as a
              Message 6 of 10 , Jan 29
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                I believe it is in gas use only. Still, what happens if the capillary tube fails? My Dometic manual also lists loss of a gas charge in the thermostat as a failure condition.

                "If the thermostat control assembly loses its charge, it will become inactive. To
                test for a lost charge, while the flame is reduced to minimum and the temperature
                control is set at a numbered position on its dial: Remove thermostat capillary tube
                from its clamp in the evaporator and warm capillary end with the hand, If the flame
                fails to increase in size, the thermostat has lost its charge and the thermostat
                must be replaced"
              • red2dog45
                My mistake in terminology. What I was referring to is the capillary tube that senses the evaporator temperature, and is connected to the thermostat. What
                Message 7 of 10 , Jan 30
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                  My mistake in terminology. What I was referring to is the capillary tube that senses the evaporator temperature, and is connected to the thermostat.  What happens if that component fails?


                  This a Dometic that over cools in propane mode, which I have heard of before. Trailer was just bought by a friend but not accessible yet, so exact model is not known. My own Dometic manual lists a leak in the thermostat shut off valve as a possible cause, but no mention of the capillary tube as another cause.

                • Todd Barnard
                  It should freeze if the cap tube lost its pressure. There is a brass bypass screw in the back of the T-stat that allows the flame to run on high if that
                  Message 8 of 10 , Jan 30
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                    It should freeze if the cap tube lost its pressure.  There is a brass bypass screw in the back of the T-stat that allows the flame to run on high if that happens...that way your food freezes, rather than spoils. 

                    If the refer runs ok on Elec, but not gas, then the T-stat could be weak, gas pressure could be off, burner could be dirty, the flue could be dirty or there could be a blockage in the ventilation at the outside...ie the roof vent.

                    With the separate T-stats for each fuel, you need to tackle each fuels problems individually.

                    I can give you a step by step on tackling this tomorrow...off to bed now!

                    Do you have a way to check the gas pressure?  A manometer?


                    On Thu, Jan 30, 2014 at 12:19 AM, <red2dog45@...> wrote:
                     

                    I believe it is in gas use only. Still, what happens if the capillary tube fails? My Dometic manual also lists loss of a gas charge in the thermostat as a failure condition.

                    "If the thermostat control assembly loses its charge, it will become inactive. To
                    test for a lost charge, while the flame is reduced to minimum and the temperature
                    control is set at a numbered position on its dial: Remove thermostat capillary tube
                    from its clamp in the evaporator and warm capillary end with the hand, If the flame
                    fails to increase in size, the thermostat has lost its charge and the thermostat
                    must be replaced"


                  • red2dog45
                    My guess is the t-stat shutoff valve is leaking from crud (easily cleaned in some models) or not closing because the cap tube has lost pressure. Some have a
                    Message 9 of 10 , Jan 30
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                      My guess is the t-stat shutoff valve is leaking from crud (easily cleaned in some models) or not closing because the cap tube has lost pressure. Some have a dual gas/electric thermostat rather than separate systems like my own. The dual unit may only use one cap tube.

                      Am finding out the exact model # and will download a manual. I don't have access to troubleshoot until March when the present owner turns it over to the new purchaser (friend of mine).

                      I do have a precision Dwyer Magnehelic in 0-15" w.c. set up to do this kind of testing on an RV.or residential gas system. I have 35 years experience with industrial gas delivery equipment. Most of it for extremely hazardous materials used in Semiconductor manufacturing.
                    • Todd Barnard
                      ... That should be fine Red, we re looking for 11 wc on these rigs. you can easily test what the reg is set at, if its dropping too much, and if there is a
                      Message 10 of 10 , Jan 30
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                        On Thu, Jan 30, 2014 at 2:03 PM, <red2dog45@...> wrote:
                        Dwyer Magnehelic


                        That should be fine Red, we're looking for 11"wc on these rigs.  you can easily test what the reg is set at, if its dropping too much, and if there is a leak in the system.

                        Of course, the one factor I did not mention before, is leveling. Some refers are more affected by this than others, and tend to be fussier on gas due to the extra accumulation of heat it generates in the rear compartment.

                        Cheers, Todd.
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