Surburban Furnace - 2014 Rockwood 2618W

[2ags81]

Just started to look into this problem, so do not have much specific info (model number, etc.). Furnace is mounted under dinette seat. Have not yet tried to remove, open case or otherwise diagnose. Our unit has been in covered storage for approx. 8-mos. Brought home yesterday to clean and test all systems. Everything clean and working fine except the furnace. I have the bug screens on the outside of trailer. Opened propane tank (definitely has propane - get green indication on tank selector and burners on stove flowing/burning good), set thermostat to heat, blower ran and unit started to provide heat just as it should, but after short time it shutoff and now when we try it again only the blower will run before unit shutdown (no igniter clicking sound, no ignition). After the first run (when it ran for short time), we smelled what seemed like a very slight burned plastic smell. I'm thinking that one of the switches has burned out (sail switch???). Any help greatly appreciated.

[Bama Rambler]

If the blower is running, but it isn't trying to ignite it's possibly the sail switch.

Have you tried pulling the fuse for a minute or two, replacing it and then seeing if it'll light?

[5picker]

Are you connected to shore power or running off battery?

After 8 months in storage maybe the battery is low enough it won't run the fan in the furnace fast enough for the sail switch to operate properly.

Have you done any voltage checks?

[MR.M]

over the net diag with limited info . things to check sail switch continuity through switch when blower on . spark yes or no ? no spark hi-limit take off cover back of unit and test continuity through switch . blower comes on sail switch chaecked and good hi-limit checked and good bad board

[2ags81]

Thanks - have RV on shore power at my house.

[2ags81]

Thanks - sail switch was my first thought - on my particular furnace SF-30FQ (vintage 2014/2015) I cannot find the sail switch. I do not see anything that resembles what I am seeing in You-tube videos. I finally figured out how to remove the furnace so that I could better examine. It's very weird, but now instead of the blower motor going off after about 20 secs, it stays on and won't go off unless I turn thermostat to off and trip breaker. then when I cycle breaker back on, the blower will be off. Still no spark.

[rvdoctor]

Once the furnace is removed try installing the outside exhaust/intake into the furnace. Sometimes an airflow turbulence problem occurs when the exhaust assembly is not installed and furmace will not ignite. Check voltage at furnace then connect the two blue wires(tstat wires) together. If furnace runs then the sail and high temperature limit switches can be checked. If furnace does not run check relay or circuit board relay depending on furnace model, for power to motor. If furnace will not shut off after heat cycle check relay to make sure it cuts power to motor. Also check exhaust and intake for any obstructions, igniter for proper clearance and gas valve if furnace does not fire.

[5picker]

Here is a link to the service manual for that model.
It has a pretty detailed troubleshooting section.

The furnaces are really pretty simple.
A few tests should have you going in the right direction.

Suburban Furnace Service & Training manual

[2ags81]

Furnace now running normally - I tested the sail switch and the limit switch and voltages and continuity. Made sure all wire connectors were tight and everything was clean. Everything checked out. Reconnected gas and tested. If it didn't work figured I would just order the replacement control board, but to my pleasant surprise furnace has been working / cycling normally since this afternoon. The only thing I can figure is that a connection was loose. Frustrating, but I sure did learn a lot about Suburban RV furnaces! Thanks to all who responded. Happy New Year!

[Bama Rambler]

Thanks for coming back and letting us know that you got it fixed. Since you didn't find anything else it could have been a loose connection or simply that the sail switch was stuck and jostling freed it up.