We have been renovating a 29' 1976 Airstream. 18 months ago I installed a Suburban NT-34SP furnace. Did all of the measurements for the ducting and installed per the instructions. First time we fired it up it worked and has kept us warm even when temps get into the single digits (F).
It has continued to work for the past 18 months but yesterday it started doing something odd. When I move the thermostat up to 75F the fan goes on and air can be felt coming through the ducting at both ends of the trailer. After about 15 seconds there is a click. The air and ducting actually get slightly warm and then cold as it cycles through for 10 minutes before the fan shuts down.
Took the front cover off. No extra parts laying around and fan is pushing lots of air out of the open end. Looked through the flame "port hole". The flame is visible but then it stops and then it restarts. It goes through this cycle for 10 minutes and then the furnace shuts down.
The flame looks like the drawing of the "Incorrect Flame" in the Installation Instructions. Conclusion is that it is getting 12V
and propane (tank is full) but for some reason the flame is not burning like the image of the "Correct Flame". Thinking that it may be an air bubble I have restarted the furnace many many many times. Does not seem to have any effect on the flame.
Any suggestions welcome. Fortunately we have two 110V heaters that are working so we are not desperate - yet.