Duo Therm problems

[tjseven8]

Hi, I have an old 1987 Duo Therm furnace in my kit companion travel trailer. It will cycle and work fine for about two to three hours. Then it fails to ignite and the combustion motor continues to blow cold air until I shut the furnace off. If I wait three hours or so the furnace will then operate well for another two hours. The furnace is old but it has had very little use. The intake fresh air and outlet vent is clear to the unit and the propane supply is not an issue. I don't think it is a limit switch because the unit cycles properly and does not appear to get too hot when it is running well. Any suggestions? Thank you for any help!

[Cougarkid]

Check the burner.

One in our 89 GBMC had the same issue before. I ran down all the other options before discovering it was bad. Seemed strange that it worked for a while and then stoped, but it solved the problem.

You will have to unhook the propane line, remove the exhaust tube, unplug some wires and take out 5 (I think) screws to get the propane valve out with the burner attached to it.

Mine was blown apart, with a large hole in the middle.

New, it should look something like this:

[Ray,IN]

Sometimes low voltage will cause the fan to run slow, which in turn causes the sail-switch shut off the LP. Make sure your house battery is good and fully charged, and all wire connections are clean with good contact.