Roo 17 - Furnace Problems - Shuts Off After 10-12 Seconds - No Ignition

[skyhawk133]

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 posted recently.

Problem: Furnace blower comes on for 10-12 seconds, then turns off without igniting.

Replicating: 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.

Troubleshooting: 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.

Temporary Solution: 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)

https://www.youtube.com/watch?v=gUPRPww7CLk

Video 2: Shows furnace working with cover off, but not with it on

https://www.youtube.com/watch?v=CKVvknxHvhw

Video 3: Shows furnace working with vent covers off, but not with them on

https://www.youtube.com/watch?v=OlSh6eoobag

[rockfordroo]

You've got some pretty tight turns in your duct work. You may even have an internal crimp/collapse in one (or both) of them. This would reduce the air flow. It may be reduced just enough to cause the sail switch to trip. Removing the vent covers allows it to increase just enough to not trip the sail switch. With the vent covers off, look into the ducts with a flashlight and see what you can see. You might have the worst of both: crimped ducts and a tight sail switch working together.
You might want to go to Home Depot and see if you can get some real elbows to make the turns, although I'm not sure you've got enough room for an elbow.

Unless you've got small animals, leaving the vent covers off shouldn't hurt anything for the time being.

After some additional sleuthing: It looks like both of those vent ducts come out pretty close together; one coming through the end of the dinette bench and the other between the bench and the bathtub in the bathroom. Looking at some RV dealer pics of Roo 17's, it looks like you've got a vent panel under your bathtub, but no vent. See a similar panel with a vent in it in the pic of the shower in my Mini Lite (My Roo 19 had a similar vent duct, but I don't have a pic of it). So another option you might consider is to move the duct that runs behind the bathtub so it comes out from under the bathtub in the bathroom. This would keep your bathroom warmer, while reducing the length of the duct run and probably reducing that 180 degree turn to a 90 degree turn. The down side is that it could make the rear bunk area colder, though. (But this is how it worked in my Roo 19; unfortunately, we never used the rear bunk, so I don't know if having heat in the bathroom made it colder in the rear bunk.) OR you could put a wye in the duct and feed both the bathroom and the original duct.

[skyhawk133]

I think we figured out how to replicate it. It only seems to happen when the batteries are about 2/3rds full or less. So when the dealer gets it, the batteries are typically full and they can't replicate. I'm gonna run the batteries down in a couple weeks and take it in.

So I'm guessing either a bad blower, or a bad sail switch (or one that needs adjusted) I think is the problem.

I'm not 100% sure the high altitude has anything to do with it yet (low oxygen), but going to see about testing it when I get it home next time after I run the batteries down some (I'm at about 5,000ft, we camp at 8,000ft).

[rockfordroo]

Thinner air at high altitudes isn't pushing the sail switch as hard.

Assuming the sail switch is like everybody else's, I suspect you've got a trifecta:

1. Low battery = lower fan speed = lower fan flow
2. Hi altitude = lower density air = lower flow pressure
3. Crimps/turns in duct work = high flow resistance

You can't fix #1 unless you get solar or generator to keep the battery fully charged.
You can't fix #2 unless you don't camp at high elevations.
That leaves #3. Figure out how to make the ductwork smoother with fewer turns if possible.

[jhoppmann]

Weve gone on 2 trips in our Rockwood 2306. first trip was at 7000' on battery power and we had the same heater symptoms. We just did our second trip to a campground a few miles from the first place and had no problems with the heater but this place had 30A hookups....

[jhoppmann]

Update with another 2 trips.

7000' campsite on battery power and covers on = heater will not ignite
7000' campsite on battery power and covers off= heater works fine
7000' campsite on shore power and covers on or off = heater works fine