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Old 01-14-2009, 06:30 PM   #1
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al_in_cedar
is it the Thermostat? 1985 T-1350

okay, i searched the forums and didn't find an answer to this question...

FIRST: Im a newbie.. let me get that out of the way... I just picked up a real nice 1985 Sunline T-1350. It's exactly what I've been looking for and in very good shape. ($900)

Here is the problem.. I KNOW the furnace works(ed). I can light the pilot light and have actually had it fired up and had it heating. However... I kind of tapped on the thermostat a couple of times and the heater stopped heating.

Here is what I can tell you:
1. the pilot light is lit and is very easy to light and STAYS lit.
2. the stove works fine.
3. the fan kicks on when I want it too and turns off as it should.

the only thing missing is the FLAME part which provides the HEAT part.

I am thinking that the thermostat stopped working when I 'tapped' on it. Although there isn't much to it, I dont know anything about it...

Anyone out there that can throw this newbie a bone and tell me what to try? If it's just the thermostat, i'll run out to the thermostat store tomorrow, but I need some input from the pro's...

All in all, I'm real happy with my purchase and I think I have a real nice box..

THANKS IN ADVANCE
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Old 01-14-2009, 11:29 PM   #2
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H'mm a 1985 unit. Do you have a model/make number of the furnace? I can attempt to look it up.

And any pics of the unit where the gas valve/pilot light is?

This much it "sounds" like. Tell me where I go wrong.

The pilot lights and stays lite? This older one you have to actually lite the pilot. This means the thermocouple is OK.

The fan runs but does not lite. Well the T stat is 1/2 working or the fan would not run.

I really need to see the model/brand you have and what vintage it is. The old ones where pretty mechanical and the gas valve sort of ran the show. The new ones are electric controls.

Let me know what you have and may be able to help further.

Oh, welcome to the club. Glad to have you with us.

John
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Old 01-15-2009, 08:44 AM   #3
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Sail Switch

Assuming the following, the pilot is lit, the pilot knob is turned to ON, the white switch is on at the thermostat and the temperature is set above the ambient.

From your description all these conditions have been met because the furnace's blower is working indicating the thermostat is working.

The final element is the sail switch, a small mechanical switch with a 'sail' on it. It is used to detect that the blower is running before the furnance will turn on, the air blows on the switches sail and closes the switch.

Is there a schematic of your furnace under the front cover showing the sail switch? If you can find the wires that go to and from the sail short you can jump out the sail switch and if it works the problem is the switch.

I also might consider loosening and retightening the screws on all the wires. Sometimes in these old trailers you get contact corrision; similarly if there are any slide on connections.


Norm Milliard
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Old 01-15-2009, 01:30 PM   #4
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If there is no air conditioning in the unit, then the thermostat is most likely the old style thermo-mechanical switch. The ones I remember had a coil of metal to sense the temperature, and a mercury switch. When the coil expanded or contracted, it changed the tilt of the mercury switch to the point that it turned on or off. The temp set lever or dial adjusted the position of the switch/coil in a circular fashion.

If that's the type of thermostat that's there, then I believe those are two wire (+ & -) and the thermostat can be bypassed by either jumpering the wires, or leave the cover off and turn the temp up so that you can see the mercury cover both contacts inside the little glass tube.

Short of physical damage to the thermostat, they just don't wear out. But as Norm stated, dealing with corroded connections is an absolute must.

There's a second kind of thermo-mechanical thermostat that just has a tab of bimetal (moves based on temp), and a slider to adjust the set point. Based on the temp, the tab bends until it touches a contact, making or breaking the circuit. This type of thermostat can wear out due to corrosion on the contacts and just plain metal fatigue. But again, if it is two wire, it's no problem to jumper the wires to insure that the furnace is set to run while trouble shooting.

If you determine that the thermostat needs replacing, I would recommend the Hunter digital conversion ($20 at Wal-Mart). It's easy to do and costs much less than replacing an RV specific thermostat. It is much more accurate than a thermo-mechanical one, and gives a easy to read temperate display even when not using the furnace.

The sail switch and gas knob to ON are the primary areas I'd look at.
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Old 01-16-2009, 10:13 PM   #5
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Re: Sail Switch

Quote:
Originally Posted by Honda03842
Assuming the following, the pilot is lit, the pilot knob is turned to ON, the white switch is on at the thermostat and the temperature is set above the ambient.

From your description all these conditions have been met because the furnace's blower is working indicating the thermostat is working.

The final element is the sail switch, a small mechanical switch with a 'sail' on it. It is used to detect that the blower is running before the furnance will turn on, the air blows on the switches sail and closes the switch.

Is there a schematic of your furnace under the front cover showing the sail switch? If you can find the wires that go to and from the sail short you can jump out the sail switch and if it works the problem is the switch.

I also might consider loosening and retightening the screws on all the wires. Sometimes in these old trailers you get contact corrision; similarly if there are any slide on connections.


Norm Milliard
Adding to Norms point on the sail switch, that is if yours has it. The battery on the camper needs to be charged enough to make the blower run fast enough to make the sail switch close. Or you need to be plugged into shore power and then the blower is running off the converter and has enough volts to run fast enough.

Even the new campers with DSI will stop the fire (gas valve) if the battery drains down too far, the wind cannot trip the sail switch and then the flame goes out.

Something to check if yours has a sail switch and you are running off battery only.

Try and find a Model number. I found a 1985 manual on a Hydrotherm but do not know if it is your model.

John
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