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Sep 18, 2006
I have a t/t that is 3 years old. It has a forced heater and a single a/c .Both are controled bt a DUO THERM thermastat. On a recent trip,the heater would not turn on. The a/c works as well as the fan.
Is there a way to test a thermostat? I have checked the fuses etc.. Thank You
If the furnace fan comes on when you turn up the thermostat, it may be that the furnace is not igniting.  Verify that the gas in turned on.  The igniter on the furnace may be defective or have some contamination. 
thanks for the reply but the heater fan does not come on. I place the thermostat on furnace, turn up the temperature to get the fan to start but nothing happens. I can hear a relay switching when I move the temp up and down. I get a "Clicking " sound but nothing happends with the heater. The a/c works fine.
I there a way of by passing the thermostat and fire up the furnace??  the thermostat is a duo therm wih 6 wires. RED 7.5 volts dc, BLUE wire is high fan, WHITE = furnace,BLACK =ground, Yellow= a/c , ORANGE = low fan......????
There may be a fuse or two on the furnace controller board mounted in the outside access panel. If you hear a clicking sound but the blower doesn't come on, check those fuses. Also check the blower to see if it turns freely. Without the fan running, the sail switch will prevent the furnace from lighting regardless of what you do with the thermostat. If the rig sat for a long time without the furnace running, critters may have built a nest inside the blower housing preventing it from turning. Even if you could get the furnace to light, it wouldn't do any good without the blower running, and you run the risk of overheating or fire if it gets too hot. There is a high temperature limit switch to prevent that from happening, but I wouldn't count on it.
Well, I removed the access panel that is located inside of the trailer and there were no fuses there. I checked around the wires going into the furnace and did find a red wire that had been broken off. The other end of the wire was still contained within the wire connector. I reattached the red wire and still no furnace. I did notice that the clicking noise had stopped after re-attaching the red wire.
The blower wheel turns freely.
There is no other access panel that containes any type of circut board both inside the trailer or from the outside.
OK guys, I guess the broken wire did the trick.

After making the connection and trying it with no change, I got to thinking,  Dang, I'm hot and sweaty fixing this thing. Its must be 100 degrees in here! Then it hit me right in the head. The reason its not firing up is because its too hot in the trailer and the thermostat only goes up to 90 degres!
So I ran the a/c for about 10 min and brought the temp inside way down. WA LA!! the furnace fired right up blowing nice hot air.

Thank you for your input and this forum is really helpful. Not just with my problem but reading everyone Else's questions etc.

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