Good morning everyone, hope you're all anxious to hit the roads this summer !I've got a problem with the built in heater in my old 1980 Holiday 20' travel trailer. It's just a "hot box", not a forced air system. When we first got the camper, the temperature adjustment knob would turn but not "click" the thermostat to a temperature setting. I've since adjusted the knob to make the heater turn on & off, so now it's at least functional.The problem is, the thermostat doesn't actually do anything. Turning the knob turns on or off the burner, but the thermostat (a pen-sized tube attached to a hard copper temperature signal wire) doesn't seem to actually do anything. No matter where the temp is adjusted to, the unit is either on, or off.Does anyone know anything about testing or replacing the thermostat, or if anything on the unit is adjustable to make the thermostat functional ?I'll go grab a model # later today, don't have it handy.Thanks in advance all.

After you grab a make and model number the group here will be able to help you more. But, I just wanted to warn you that I once had a older TT and I found they did not make parts for the furnace anymore. Sucked too, I loved that style of furnace. You may be able to get parts for yours I'm just warning you to not be surprised if you can't.

Is it a mercury based thermostat or does it have a bi-metal coil?

westend wrote:Is it a mercury based thermostat or does it have a bi-metal coil?Couldn't say. It's a Hydro Flame Furnace Model BRC-10A, 10000 btu input, 7000 btu output. Originally the thermostat was horizontal just above the floor level, I moved it up vertically next to the furnace (no difference).Is it possible that the thermostat must remain horizontal, in order to function ? Once we get out of the deep freeze (it's -20°C with the wind today) I'll fire it up and put heat to the thermostat with a hair dryer, just to see if it actually does anything. I'd like to look at some other way to activate the thermostat, either with an external electric deal or some other way. Someone somewhere must have gone through this and come up with a solution .....

I would bet that the tube contains mercury and yes, it needs to be mounted on an exact angle to function. Mercury thermostats are no longer being made so be careful with it. Could it be that the initial testing, before you relocated that tube, were done with the trailer off-level? That may have contributed to it's non-function. Where is the knob part of this to adjust?

Its on the off/pilot/on valve block behind the swing open panel at the bottom (where you light the pilot). Separate knob for temperature control, very much similar to manually lit water heaters.The thermostat was pretty level with the floor, but not much in there is level with anything else, if you catch my drift .....

Built in Propane Heater thermostat not functioning

CavemanCharlie
Explorer III
Apr 08, 2016
After you grab a make and model number the group here will be able to help you more.

But, I just wanted to warn you that I once had a older TT and I found they did not make parts for the furnace anymore.

Sucked too, I loved that style of furnace.

You may be able to get parts for yours I'm just warning you to not be surprised if you can't.
westend
Explorer
Apr 08, 2016
Is it a mercury based thermostat or does it have a bi-metal coil?
denis007
Explorer
Apr 08, 2016
westend wrote:
Is it a mercury based thermostat or does it have a bi-metal coil?

Couldn't say.

It's a Hydro Flame Furnace Model BRC-10A, 10000 btu input, 7000 btu output. Originally the thermostat was horizontal just above the floor level, I moved it up vertically next to the furnace (no difference).

Is it possible that the thermostat must remain horizontal, in order to function ? Once we get out of the deep freeze (it's -20°C with the wind today) I'll fire it up and put heat to the thermostat with a hair dryer, just to see if it actually does anything.

I'd like to look at some other way to activate the thermostat, either with an external electric deal or some other way.

Someone somewhere must have gone through this and come up with a solution .....
westend
Explorer
Apr 08, 2016
I would bet that the tube contains mercury and yes, it needs to be mounted on an exact angle to function. Mercury thermostats are no longer being made so be careful with it. Could it be that the initial testing, before you relocated that tube, were done with the trailer off-level? That may have contributed to it's non-function. Where is the knob part of this to adjust?
denis007
Explorer
Apr 08, 2016
Its on the off/pilot/on valve block behind the swing open panel at the bottom (where you light the pilot). Separate knob for temperature control, very much similar to manually lit water heaters.

The thermostat was pretty level with the floor, but not much in there is level with anything else, if you catch my drift .....
westend
Explorer
Apr 08, 2016
That copper pipe is not a thermostat. I would bet that it is some type of expansion tube for a limit switch. These old furnaces are beyond my pay grade but practical sense goes a long way. I'd suggest to locate that pipe as it was originally and to inspect the thermostat/valve combination. It may be that the adjustment is only for the amount of gas fed to the burner and you really don't have what would be considered a true "thermostat".
denis007
Explorer
Apr 09, 2016
I plan to replace it as it was, but I'm sure its a temperature sensor of some kind. It's a solid copper wire, think way back to old analog outdoor thermometers that the sensor lead was a solid copper wire, same idea. I would think that the lead transmits temperature info in analog format to the control knob.

The temperature control has a distinct click feel when turned, at which time the burner turns on or off. I can't say that I've ever noticed that point being in a different place relative to camper temperature (temperature doesn't affect or move in relation to the knob setting) .

Going to do some searching tomorrow morning on the 'puter, for some technical info on the thing .....
denis007
Explorer
Apr 10, 2016
westend wrote:
I would bet that it is some type of expansion tube for a limit switch.

It would seem to be in fact an expansion tube. What it does and how it works (in detail) is still a mystery, one I've not been able to decipher yet, but I did learn a few things while searching last night.

Looking like next weekend will be good weather for piddling around with it, may go as far as removing the combustion chamber and cleaning it out properly. At the very least I'm going to re-install the tube as it originally was (and properly levelled) and test it for functionality.
SprinklerMan
Explorer
Apr 11, 2016
Looks like a thermo coupler . On a home hot water heater or furnace the flame heats it . Its function is to keep the gas valve open .If it becomes cold it will shut off the gas valve . Its usually kept hot by a pilot light .
denis007
Explorer
Apr 11, 2016
SprinklerMan wrote:
Looks like a thermo coupler . On a home hot water heater or furnace the flame heats it . Its function is to keep the gas valve open .If it becomes cold it will shut off the gas valve . Its usually kept hot by a pilot light .

The thermocouple is on the pilot light, this is external to the furnace. In an old manual I found online they call it a "Sensing Bulb", and it's to be mounted horizontal below the furnace grille.

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