Furnace issue

Have a look at this video. It sure sounds like your problem.

Sail switch failure.

Exact same symptoms if voltage to the furnace is low-- the fan does not turn fast enough to close the sail switch.

Same if either return or outlet vents closed/blocked-- reduced air flow causes sail switch to not close.

It can be a lot of different things based on what got stated. Best thing to do is go outside by the exhaust. Have someone turn on the furnace and smell for propane after a loud click, then listen for several smaller clicks (igniter.) This will rule out a lot of things. If you can't smell or hear things that will direct you to the problem.

Also prior to doing the above, cycle the furnace on and off a half dozen times to make sure the air is purged from the line.

Are you on shore power or battery? If on battery, voltage maybe too low to get fan up to speed to close contacts on the sail switch.
Could be dirty contacts on circuit board connector.
Check the flame sensor/ ignitor for proper clearances
Make and model of furnace would be of help.

We always make sure the Battery is up ok even if we are on shore power and also always run the propane cook stove burners for a minute or so to purge the air from the lines...

Normally we also hear the furnace click trying to start the furnace. If it clicks three times without starting it shuts down...

Roy Ken

Well many times it is a faulty sail switch that has to be replaced.

I had the same similar symptoms with me rear furnace.... fan would come on and it wouldnt light blew it out and it didnt help.Then one day while out at the races pulled the cover and ended up pulling circuit board out to look at it and check connections.Board looked fine except for the back side of board was covered in a nice layer of dust.I blew it off and wiped the back of the board off to clean it .Put it back together and it has worked ever since.

We have a Harney Coach Works 37' diesel pusher. Back in 2006 we were in Michigan over T-giving and the furnace started working as you describe. Mobile tech found one of three LN125 amp fuses blown. Replaced it and furnace has worked (knock on wood) since.

outofplace wrote:
I had the same similar symptoms with me rear furnace.... fan would come on and it wouldnt light blew it out and it didnt help.Then one day while out at the races pulled the cover and ended up pulling circuit board out to look at it and check connections.Board looked fine except for the back side of board was covered in a nice layer of dust.I blew it off and wiped the back of the board off to clean it .Put it back together and it has worked ever since.

I had this happen several years ago, now it's on my annual prep list.

Fred