Would like to pull furnace to check igniter

[Bkrhoda]

Hi everyone! We have a Solitude 380FL-R. Experiencing issues where the furnace (Suburban SF-35VHQ) will come on as requested. Blower spins up, can hear the igniter fire and burner starts, briefly. About 15ish seconds later it will try to re-ignite, can hear the "pop" of the gas lighting, but still no heat. It tries a third time, usually fails & goes into lock out mode. I can reset it via the thermostat and start the cycle again. Usually have to try this for 2 - 4 cycles before the ignition holds and we get heat.

Following the trouble shooting flow chart, it would appear that the most likely suspect is the igniter/flame sensor. Could be sooted up or knocked out of alignment by the stellar roads we've experienced wandering around the southwest this fall.

Had a sail switch fail last year, that was a piece of cake to replace. For this one, does anyone have any tips for removing the furnace so I can get to the igniter cover? In the 380, the furnace is installed beneath the water heater and there is ZERO inside access. I'm a mechanically inclined electrical engineer, willing to invest some sweat equity to make a repair.

Is this an instance when I should take a humble pill and call a service tech? We're headed back north to upstate NY in a month and figure we may need the furnace to make those cold northern nights tolerable!

 

[Riverbug]

Not familiar with your specific model. Sounds like if you had the time you could do it yourself. If you want a quicker job done, maybe it would be better to call a tech out. Good luck!

 

[KollerKruizin906]

I had a similar issue and the cure was replacing the main regulator after the tech replaced the igniter which didn’t cure the issue. Regulators are inexpensive and easy to replace. Keep in mind your furnace draws a lot of gas and even if your stove, and other propane appliances work just fine your furnace will pull 3x what your stove does and tax a faulting reg. Separately, I found rvrepairwoman.com YT channel great at providing focused furnace troubleshooting and repair. I have no affiliation with her, just found after 4 years of being FT she is concise and to the point.

 

[Scott'n'Wendy]

I'm going to suggest it isn't your ignitor. I would investigate/verify gas flow and air flow first. Ignitor/sensors are pretty durable devices and the pop noise of the flame out was caused by a fuel air ratio problem imo.

 

[gfl123]

i had something similar, sticky sail switch, paid a service tech a couple hundred to fix it, only to have other similar issues a few months later. I ended up finding a decent deal on a whole new unit ($600ish) changed it out myself and never had any more problems.

my only point is, weigh the cost of fixing it or paying to fix it vs just replacing the whole unit.

 

[Bkrhoda]

I had a similar issue and the cure was replacing the main regulator after the tech replaced the igniter which didn’t cure the issue. Regulators are inexpensive and easy to replace. Keep in mind your furnace draws a lot of gas and even if your stove, and other propane appliances work just fine your furnace will pull 3x what your stove does and tax a faulting reg. Separately, I found rvrepairwoman.com YT channel great at providing focused furnace troubleshooting and repair. I have no affiliation with her, just found after 4 years of being FT she is concise and to the point.

There is only a valve on the furnace itself, so I'm guessing you are referring to the regulator that is in-line after the tank selector, yes? Much easier to work on, for sure.

 

[toolman.dustin]

I'm going to suggest it isn't your ignitor. I would investigate/verify gas flow and air flow first. Ignitor/sensors are pretty durable devices and the pop noise of the flame out was caused by a fuel air ratio problem imo.

I agree. Often, when a gas flame won't ignite or stay lite, there's an obstruction in the air inlet tube next to the gas flow tube. You can look, but you might not see it. Just take a Q-tip and wipe the inside of the tubes to remove any dust, hair, cobwebs, etc. If you have pets there's a good chance it's hair and dust that got sucked into the air inlet.

Dustin

 

[Bkrhoda]

i had something similar, sticky sail switch, paid a service tech a couple hundred to fix it, only to have other similar issues a few months later. I ended up finding a decent deal on a whole new unit ($600ish) changed it out myself and never had any more problems.

my only point is, weigh the cost of fixing it or paying to fix it vs just replacing the whole unit.

I had a bad sail switch last year - piece of cake to replace that. My current issue is compounded by the fact that I have no internal access to the furnace. I can remove the outer cover, loosen the mounting screws, but that's it. Furnace is installed under the water heater (odd choice there) and the only way I can see to get access to ducting, etc. is to drop the choroplast (?) and work from the bottom up. Not fun.

Looking to see if some buds here at the park have a manometer, that will let me check the LP pressure getting to the furnace.

We're currently down near Brownsville, TX. It was over 100 yesterday and will be near 90 again this week. Running the furnace isn't a current issue, but the trek to Upstate NY starts in 3 weeks. Might need a little heat in the mornings once we return to the tundra!

 

[Scott'n'Wendy]

If you have access to compressed air...a shot through the burner tube may clean out any spider nests etc that may be impacting air flow. For gas flow, if no manometer is handy, try switching over to the other tank. See if it makes a difference.

 

[Bkrhoda]

Furnace behaves the same on either tank. I only have a Viair compressor, but will check around the park for a tank compressor. Manometer will be in hand in a couple days. Regulator is still a leading suspect.

 

[Bkrhoda]

Got a manometer today. Installed it on the gas line right at the furnace. Measured a whopping 7 inches of water column. Minimum is 11. New regulator will be here Saturday. Temps then will be pushing 90 here. But when we get back north May 1, we'll still need the furnace for sure.

 

[Chaps2018]

Thanks for the closure post.

 

[Bkrhoda]

Wellll, the new regulator didn't fix it. Still having the same issue with having to reset multiple times to get the furnace to fire and stay lit. To recap - the furnace will try to light. I can hear the "pop" of the ignition. That eliminates the limit switch and sail switches as the problem. I did rig up my leaf blower to directly blow through the combustion chamber. Didn't see and debris come out (spider web or wasp nest). Tested furnace again - same results.

My real question now - what does it take to pull the furnace? No easy interior access. Does the rear of the furnace back into a plenum or are there 5 or 6 individual ducts connected? Will I have to climb into the storage bay and pull the wall off behind the nautilus panel? I'm a larger guy, this will be a challenge. I've seen these SF-35's with a compressible gasket on the back that just mate to a plenum - really hoping that's how the 380 is set up. Anybody know?

I have an igniter, module board, burner and burner access gasket coming today & plan to play with it all tomorrow.

 

[Tom Traveler]

Wellll, the new regulator didn't fix it. Still having the same issue with having to reset multiple times to get the furnace to fire and stay lit. To recap - the furnace will try to light. I can hear the "pop" of the ignition. That eliminates the limit switch and sail switches as the problem. I did rig up my leaf blower to directly blow through the combustion chamber. Didn't see and debris come out (spider web or wasp nest). Tested furnace again - same results.

My real question now - what does it take to pull the furnace? No easy interior access. Does the rear of the furnace back into a plenum or are there 5 or 6 individual ducts connected? Will I have to climb into the storage bay and pull the wall off behind the nautilus panel? I'm a larger guy, this will be a challenge. I've seen these SF-35's with a compressible gasket on the back that just mate to a plenum - really hoping that's how the 380 is set up. Anybody know?

I have an igniter, module board, burner and burner access gasket coming today & plan to play with it all tomorrow.

Well, I hate to break it to you, but if your Suburban furnace is like the one (SF-35Q) in our 2021 380FL-R, you’re going to be getting into the area behind the storage area panel. In ours, the 5 ducts are clamped to the rings on the plenum back plate. The plate comes off with some screws on each side. Inside, there are several screws going through the floor of the furnace cabinet into the floor of the RV. Once those are out and after you remove the outside trim plate, you should be able to slide out the furnace.

I’ve attached the installation manual for these furnaces. As far as I know, the only difference between the 35Q and the 35VHQ is that the VHQ can also be installed vertically.

 

[Bkrhoda]

Thanks for the bad news Tom!! I was afraid of that. I'll have to empty out that cubby (opportunity to sort & throw out stuff!) and wedge my body in there. The options I have left for faulty components forces me to yank the furnace. All the parts came today (5/6), 5/8 I'll be diving in.

Thanks for the install manual. I also hit up Suburban for the parts manual. If you'd like a copy, let me know & I can send it to you. It's too large to attach.

 

[Bkrhoda]

Resolution!! Got all my spare parts, got a day to play. Yanked the furnace, got it out of its shell and took it inside to go to town (it's in the upper 40's low 50's here for a few days) Opened up the burner chamber and really didn't believe what I saw. The burner looked tortured. It was so warped & distorted it was hard to pull out. In the pics, see if you can guess which is the new burner.

Got everything put back together, reinstalled the furnace and tested. Success!! 3 for 3 on first time starts. The bad news? I just touched the pex tubing behind the Nautilus panel and think I've found 3 or 4 leaks. Got one fixed, but I had to give my body a rest. Time to dive back in and fix a few more leaks. Then the bourbon therapy can start!!

 

[Chaps2018]

Wow, maybe a substandard material was used???

 

[Bkrhoda]

There was actually slag bits that came out when I tipped it on end. Wondering if it started with one bad spot, then started burning poorly & developed hot spots. No wasp nests, no spider webs. Glad its fixed, & now I have the leaky pex joints fixed too. Oh my aching back!!