Sf 35 furnace

[Quietcorona]

Hey everyone. I have a bit of a tale and some help that may be needed. Late fall I got to our permatrailer and middle of the first night, lose heat freeze and get grumpy. Turns out that the fan has died. Take the furnace out and drive it an hour up the lake to have it tested and repaired at the "local" rv place. Turns out that the board was bad. $189 bucks later I drive it back and hook everything back up and voila still no heat but now the fan runs. Problem is the fan runs constantly and won't shut off even when I turn the furnace off at the furnace. You can hear everything wanting to fire but the igniter kicks on and then off right away again. I'm kinda new at all this but I'm pretty handy. I need to know how to bench test everything and any suggestions you may have. I did pull it out and bring it home so I can get it fixed for spring. I also want to replace the thermostat which runs both the heat and ac. Thanks in advance everyone.

 

[larrytbm]

You say you can hear the ignitor sparking, so the propane jet is the most likely problem. Maybe some rust or other debris clogged the nozzle. Poor propane flow or the ignitor too far away from the propane jet and it will not light. This problem could have been created when you removed the furnace to fix the blower problem. Another problem could be with the "sail switch", this keeps the propane valve shut off if the blower is not providing sufficient air flow for safe combustion. Slow blower speed, maybe due to low voltage, obstructions in the duct, or a sticking "sail switch" are all possible problems. And yes, the blower will run continuously waiting for the burner to fire up. Some furnace models do have a timer function to shut the fan off if the burner does not light after a few minutes.
Some yrs ago, I had an intermittent issue. At lower altitudes it worked all the time, but in the mountains it would turn on one time and next time just the blower would run. Propane diffused faster at high altitude and the ignitor needed to be located just right or it wouldn't light the propane every time.

 

[Quietcorona]

Had a fix it guy out and there is propane getting to it I think it's still electrical. That's why I'm hoping for tips on how I can bench test it at home.

 

[larrytbm]

Had a fix it guy out and there is propane getting to it I think it's still electrical. That's why I'm hoping for tips on how I can bench test it at home.

Check the sail switch and the valve that it controls, could be the new board is bad as well.