We picked up our new 2015 Roo 17 a couple months ago and have really enjoyed it except for a few issues with the furnace.
The problem seems identical to the one in this thread
Furnace blower comes on for 10-12 seconds, then turns off without igniting.
We haven't been able to consistently replicate the problem. Nor has our dealer unfortunately (they haven't been able to replicate the problem at all). The furnace may work for several hours, or even an entire night. When camping at lower altitudes or warmer weather, we haven't been able to replicate the issue. But at higher altitudes, and colder temps (below 50), by the 2nd night, it starts acting up consistently.
The dealer has tested gas pressures, voltage, wiring, and found no issues.
No obstructions in exhaust or intake (brand new unit).
Battery full. Tanks full.
The first time it happened, we were COLD and I was desperate to try and get it working. We gave my 3 year old all the blankets and the rest of us were FREEZING. I took the front panel of the furnace off just to see if there was a loose wire on the igniter or something. I found that with the cover off, the furnace would work perfectly every time. Put the cover back on though, and it would do the same thing... 10-12 second blower run up, then shut off. Eventually locking itself out.
To stay warm, we ran the furnace without the cover and it worked all night. Put the cover back on in the morning, and it stopped working again.
This got me thinking, with the cover on, the blower is pushing air through the 2 vents and there is resistance. With it off, there is no resistance, and air flows freely out of the unit. So I put the cover back on and this time took the 2 round duct covers (the directional louvers) off the vents and voila... it worked. Put them back on, and it doesn't work again (see video #3 below).
This makes me think either the motor is right on the edge of producing enough air flow to trigger the sail switch and might be bad, or the sail switch is bad. Not sure which, but definitely seems like it has something to do with the amount of air moving through the unit.
Remove the vent covers or leave the cover off (not sure if this is safe or not?)
Forest River/Dealer Solution:
??? Not sure yet. Hoping with the videos below, they'll see there really is a problem now and offer a solution better than mine.
Video 1: Showing replication of problem - Blower comes on for 10-12 seconds, no ignition, showing full battery and gas (3-4 times for good measure)
Video 3: Shows furnace working with vent covers off, but not with them on