Propane Furnace issue on 1986 Chieftain 27ft

[FeralCat]

Hello all, I have an 86 Winnie chieftain 27ft (freebie!_) and I have been testing it's systems, I turned on the LPG tank, let it sit for about 10 mins to prime it u up and get pressurized. (if needed) Anyhow I lit the stove top up, works good, the furnace I cant get to light or operate, I opened access door inside and saw a little (assume gas valve) looked like it was turned out, tried it both ways, nothing, there has got to be some small thing I am missing in the procedure whatever that is , thanks all, I appreciate you!!! Tom.

[Morich]

There are small points of each type of furnace which may differ just enough to throw us off. I always like to go to written manuals for troubleshooting to avoid missing those small points. Some don't work that way but I do recommend it.
Sounds like you are new to the Rv furnace game, so a small starter clue may help.
First thing to happen on RV furnace has to be the blower starting as it then closes a "sail switch. That sail switch actually has a sail which blows in the airflow and if it does blow, the gas valve doesn't open! That avoids filling the RV with gas if the blower doesn't start!

So it doesn't sound like you have a gas solenoid problem but more likely an electrical problem.
Most furnace will reguire the thermostat to get power, then pass that signal to the furnace when the contacts say it needs heat. That starts the furnace controls calling for first passing the 12 volt power to the motor to run the blower.
After a set time like a half minute or so, the blower is up to speed and the sail switch will then let the rest of the lighting start. Part of that later section will be the gas valve opening.
A troubleshooting section of the furnace manual will show and tell you where to check each step and suggest what is not working.
I might guess the most common failure on RV furnace is the wiring gets dirty/loose or corroded, but we have to sort it in a specific order as each step should happen.
It could be as difficult as a part failed or as simple as the coach battery disconnect switch turned off!
But first step is getting the blower to start!

[powercat_ras]

Just to say same thing as Richard in a slighty different way ...

A Furnance has a fused 12 volt feed and a good 12 volt return (ground) feed.
B Thermostat sends 12 volts to the furnace on another wire to tell furnace to operate

C If A and B get satisfied then you should hear the furnace blower start to run.

D If A, B, and C then the airflow should close a switch called a sail switch that is airflow activated.

E1 If A, B, C and D then the control board will apply 12 volts to a propane valve and open propane flow to the furnace burner. This will make a "click" sound.

E2 If A, B, C and D then the control board will generate high voltage to a spark gap element next to the burner inside the furnace, and ignite the propane being fed to the burner

F There is a flame sensor next to or part of the spark gap element if the control board senses flame then all is good. If within a couple of seconds the flame sense does not happen then the control board turns off the propane valve.

G If the no flame sensed - turn off propane valve happens then a few seconds will pass to let the propane dissapate and it will start again at E. It will try this 3 times and if no signal on flame sensor on the third try the control board will stop trying and "lock out" the furnace from further tries. Lock out is generally 1 or more hours, you can clear the lock out when troubleshooting by disconnecting the 12 volt power from the furnace for a few seconds and then reconnecting.

= = = = =

As Richard said, checking connections requires no parts, do that first. You can remove the outside cover and clean, that requires no parts as well. Getting to the actual combustion chamber where the spark gap and flame sensor is requires some substantial dissassembly and in some furnaces the furnace has to be removed to do this. You can get manuals and diagrams online for your particular furnace if you feel like you have the skills to DIY it. Insects can nest inside the burner side of the furnace that has the outside intake and exhaust vents and this can prevent sparking or propane ignition or even keep the whole blower from turning.

Wasps, etc. are attracted to propane, there are screens that mount over the intake and exhaust vents of the furnace that can minimize the risk of insects entering the furnace.

Good luck