Furnace burner wont kick on..

[onespeed]

On our 2015 Solitude 320x, the burner won't light on the furnace. The blower starts up, but shuts off after a few minutes, I think because the burner not working. It's a Suburban SF-35Q. It was working fine last month when I checked it. LP tank is full (and the valve is open) and the 12V battery checks 13.5V strong. Kitchen stove and water heater both working fine. Researching tells me to check the sail switch first. I could do this if I could figure out just where it is. Looking at the unit with the access panel off, I don't see it. I'm guessing that it will have to be slid out a ways. Has anyone done this before?
I think after removing the gas line on top and some screws on the flange, it should slide out far enough to see something, without disconnecting the ductwork. I'm willing to try it, but if someone knows this procedure, I would appreciate any guidance. P.S. I don't know why these piks turned sideways on me. I don't know how rotate them......

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[Second Chance]

The photo rotation is a software glitch on the forum - not your fault.

If you search YouTube for "sail switch" and the make and model of your furnace, you will likely come up with a video that steps you through accessing, diagnosing, and replacing the switch. It's one of the more common issues with these furnaces.

Rob

 

[onespeed]

Hey thanks Rob for that info. I will post when I get this figured out.

 

[D2Reid]

It's been nearly 2 years since I tore into my SF-35Q. But if I remember correctly you can remove the fan assembly without disconnecting the propane line. I did not remove the entire furnace. I was able to pull the fan assembly from outside. Now I wish I had taken more photos. A couple of tricky things, wires were pretty short and I had to be real careful about getting it out enough to unplug the wires, hard part was getting it back together, getting that back wire reconnected. I think I finally got frustrated enough with it to splice more wire into it with a couple of butt end connectors.

Be gentle with the fan cage, it's plastic, dropping it or bumping it hard will break it. Somewhere there was a little shim tab, about 1/8 inch thick by 1/2 inch wide by 1 inch long, a little bigger than a thumbnail, don't drop that into the fan housing...

I recall a triangle shaped cover plate with 3 screws in it, another keeper screw underneath the housing that was a little hard to get to. Motor assembly slides out, then you can remove the squirrel cage cover to get to the sail switch. (pretty sure it was in there, can't remember 100%) Be sure to test the sail new switch before you install it, I got a bad one from a dealer.

Speaking of part, I ordered what I needed from PDX RV They had these cool tune up kits that had more stuff.

If you decide to replace the control board don't throw the old one out right away. I tried a couple of replacement boards and they didn't work, so I put the original back in and it worked fine ever since. Yes, I am that bad of a repairman. Anyway, 2 weeks without heat while camping in the snow, wife was sick, turned out she had pneumonia, so we pulled up stakes and went to a GD rally in Las Vegas. I messed with it for a couple of more days and then threw up my hands and fired a mobile technician. After I already sunk a couple hundred bucks into it his bell came to around $800. I have a secondary warranty policy and they paid that bill. But it occurred to me later that I could have just bought a new SF-45Q (same dimensions) for around the same price. I would have gotten a higher BTU rating, had the whole thing replaced in a day, and my screw holes for the face plate wouldn't be stripped out.

Also pay attention to the sail switch orientation before you remove it, they don't work so good when installed backward... just saying you know...

Good luck with your repair.

 

[onespeed]

Dallas- Good info here, thanks. I looked at the PDX RV link and that will help me a lot. I'll repost when I get somewhere on this.

 

[onespeed]

Well I found the sail sw. Attached to the inside of the blower cover. Had to cut wires to get to it. I'll have to put in extensions like you did. Everything looked really clean inside. The sw checked fine over the ohm meter. I found the high pressure sw on the front of the unit. It checks good also. Think I'll pull the unit tomorrow and look at the circuit board. I'd like to look at igniter also. Might end up just buying a new furnace.

 

[D2Reid]

Might end up just buying a new furnace.

Oh no, that would be too easy.

Did you down load the manual from the PDX site. It has a pretty good trouble shooting flow chart it. The other thing I ran across was a recommendation to change the circuit board out with a different brand. It didn't work. Unfortunately I don't remember specifically which board supplier it was...

 

[Just Krusen]

Well I found the sail sw. Attached to the inside of the blower cover. Had to cut wires to get to it. I'll have to put in extensions like you did. Everything looked really clean inside. The sw checked fine over the ohm meter. I found the high pressure sw on the front of the unit. It checks good also. Think I'll pull the unit tomorrow and look at the circuit board. I'd like to look at igniter also. Might end up just buying a new furnace.

Both my sail sw and high temp sw tested ok. I replaced both and the unit has been working fine for several months now. I think the high temp sw was bad. But while removing the furnace I think it got bumped and reset so testing showed it good.

 

[dodge11]

I found that you can check the sail switch can be gotten to with the heater in place , their are four screws that hold the front of the fan housing right as you look at the front of the heater .

 

[onespeed]

I found that you can check the sail switch can be gotten to with the heater in place , their are four screws that hold the front of the fan housing right as you look at the front of the heater .

I did get the blower cover removed and did check the sail sw while the furnace was still in place in the RV. It checked fine. Also I was able to remove the high temp sw on the front of the unit and it tested good also. I decided then to pull the unit and check things that could not be checked otherwise. Burner looked good. Igniter positioned correctly. Everything looks great. I did order a new sail and temp. sw anyway. A little over $10 shipped. I'm not expecting this will fix it, but process of elimination. Next will be the module board. Then, a complete new core (isn't that bad at $379). That will be last resort.

 

[onespeed]

Did finally get the furnace issue resolved. Working great now. I surmised it could have been the gas valve but didn't want to take the chance on buying another part with out being positive. New module board didn't fix it. Bought a complete core from United RV, Fort Worth. Good people to deal with. Considering the way things are now-a-days, I'll say they have outstanding service.