Originally Posted by elranas
@flybouy, yes insect screen is installed. We have two new furnaces so I don't think this is the problem. By the way, we did blow air into the combustion chamber of the old furnace to make sure it was clean and it was.
@jasin1 yes, I jumped the thermostat and the furnace is leveled. What do you mean: "flue accounted for and not recirculating the exhaust gas". No, I don't think it has a sliding heat anticipator but I might be wrong. Here is a picture of my thermostat: https://www.dropbox.com/s/l2krd2u1yr...tat.jpg?dl=0No
I'm not sure it is not a duct issue mainly because I'm confused from the contradicting data I have so far. Sorry for the poor drawing but this is how my duct system looks like:*https://www.dropbox.com/s/105themuxb...awing.png?dl=0
@chuckster57 yes, that is exactly what I did. I twisted the two blue wires to bypass the thermostat.
@flybouy I bench tested it while connected to the trailer gas line and another time connected to a new gas line -- the one you see in the video I just posted (same propane tank and I have two of them running in parallel*while connected to the railer).
I thought you said it was also doing the same thing when you bench tested it originally. I was making sure you had some sort of temporary flue pipe hooked up and it wasnít recirculating the exhaust from the flue into the return while you bench tested. I have no way of knowing your mechanical skills so I wanted to be sure you had the furnace level like itís installed in the rv and not standing on an end or tipped to one side while you tested because the placement of the limit switch could be affected by that.
I still wouldnít rule out the ductwork ..and the worst thing you could do now is rule out anything because when you refuse to look at all possibilities you can easily overlook something. Iíve had times when I was so sure it couldnít be one thing and delayed figuring it out. Itís best to start over and go through the basics.
Is there a pressure switch in the inducer motor circuit for the flue? Because that is a definite possibility that the screen as flybuoy said could be causing back pressure and opening the pressure switch.
I would check gas pressure at furnace with a manometer
Check temperature rise of furnace
Put a meter across the hi limit switch terminals and see if the switch is actually opening and shutting off the furnace when the problem occurs(connect with alligator clips)
Jump the thermostat out while the furnace is in the trailer to rule that out( if you havenít already tried that while IN the rv)