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12-10-2016, 10:23 AM
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#1
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Junior Member
Join Date: May 2011
Posts: 16
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Suburban SF35 furnace failure - HELP!
Hello,
My furnace, a Suburban SF-35, failed this weekend. I did some troubleshooting and what I came up with is the furnace is getting propane, and there is spark. The furnace will ignite for a very short second, blow a small puff of heat out the exhaust, then no heat at all. It seems like there is just enough propane expelled into the combustion chamber to allow it to ignite very briefly, then extinguishes and will not re-light.
Any suggestions as far as replacing parts?
Thanks a lot!
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12-10-2016, 11:14 AM
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#2
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Site Team
Join Date: Mar 2014
Location: Grayson County, Texas
Posts: 21,473
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Will your propane range top light and stay lit?
__________________
2015 FR Wildcat 295RSX / GMC Sierra
Nights Camped: '13 = 49/'14 = 74/'15 = 74/'16 = 85/'17 = 110/'18 = 111/'19 = 86/'20 =108/'21 = 115/'22 = 135/'23 = 78; Booked for 2024 = 69
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12-10-2016, 11:17 AM
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#3
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Junior Member
Join Date: May 2011
Posts: 16
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Yes! And the water heater works great on propane. I checked for nests and critters and didn't see anything. Seems like not enough propane flowing through the valve to sustain a lit flame. I really don't know though. And I don't want to just start ordering parts.
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12-10-2016, 11:22 AM
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#4
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Site Team
Join Date: Mar 2014
Location: Grayson County, Texas
Posts: 21,473
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Quote:
Originally Posted by Mcnitchell
....
And I don't want to just start ordering parts.
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You're right about that. Hold your place and wait for real experts to chime in with further diagnostic suggestions. Be ready to answer the question "Did it ever work right?".
__________________
2015 FR Wildcat 295RSX / GMC Sierra
Nights Camped: '13 = 49/'14 = 74/'15 = 74/'16 = 85/'17 = 110/'18 = 111/'19 = 86/'20 =108/'21 = 115/'22 = 135/'23 = 78; Booked for 2024 = 69
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12-10-2016, 12:14 PM
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#5
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Junior Member
Join Date: May 2011
Posts: 16
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Standing by. :-)
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12-10-2016, 01:19 PM
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#6
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Member
Join Date: Oct 2015
Posts: 52
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Replace the limit switch and the sail switch. Been through this mess. Both are inexpensive and just as easy to replace one as it is both. They go bad and tend to stick.
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12-10-2016, 01:47 PM
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#7
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RVdoctor
Join Date: Jun 2016
Location: South Dakota
Posts: 77
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Sail switch seems okay because if it were faulty furnace would not light. Check limit switch wire during the lighting process for 12 VDC available at circuit board. These switches are pretty reliable and don't fail all that often. Check ignitor lead connections and insulation for defects and chaffing. Check ignitor probe for cracks in the ceramic insulator and that mount screw is tight. Make sure there is good air flow out exhaust port. Unplug harness from circuit board and clean contacts on circuit board. A pencil eraser works well. If this fails then it looks like your circuit board flame sensing circuit is not detecting a flame. Have circuit board tested or just replace the board.
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12-10-2016, 01:49 PM
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#8
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Senior Member
Join Date: Feb 2016
Location: NJ
Posts: 606
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I had a similar problem which turned out to be a stuck check valve in the hose from the LP tank. Easy to get and install and as a first step probably cheaper than changing the two switches.
__________________
DrLewie
Flemington, NJ
Former: 2007 Cardinal 30W LE
Now:2018 Arctic Fox 27-5L
2008 Ford F-250 Long Bed Diesel
Total of 30 Months on the Road Since 2008
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12-10-2016, 02:20 PM
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#9
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Senior Member
Join Date: Jan 2015
Location: West Michigan
Posts: 641
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Quote:
Originally Posted by Mcnitchell
Hello,
My furnace, a Suburban SF-35, failed this weekend. I did some troubleshooting and what I came up with is the furnace is getting propane, and there is spark. The furnace will ignite for a very short second, blow a small puff of heat out the exhaust, then no heat at all. It seems like there is just enough propane expelled into the combustion chamber to allow it to ignite very briefly, then extinguishes and will not re-light.
Any suggestions as far as replacing parts?
Thanks a lot!
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Hi the furnace control board is not sensing the mili amp signal from the flame sensing rod. There are several possibility's that can cause this.
1/ The flame rod has built up a layer white rust or just regular red rust. This will insulate the rod and will interfere with the mille amp current flow to the control board. The flame rod will need to be removed and cleaned off with some steel wool or 400 grit sand paper and reinstalled.
2/ The flame rod is not positioned correctly in the gas flame and needs to be adjusted to the factory specks.
3/ Control board has failed and needs to be replaced. The control board is located inside the furnace enclosure so the furnace will need to be pulled to get to it.
Here is a link to the suburban manual in the forum library at the top of this page. It has lots of information on furnace operation and how to repair
http://www.forestriverforums.com/for...?do=file&id=67
Just had my furnace do the same thing and tracked it down to the control board. Dealership replaced the board under warranty with suburban made board. If no warranty I would replace it with a dinosaur control board. It cost less than the suburban and is made better.
Hope This Helps Tim
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12-10-2016, 03:08 PM
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#10
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Junior Member
Join Date: May 2011
Posts: 16
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Ok, so in experimenting further, I notice when the water heater is lit and actively heating water, if I turn on a stove burner the flame barely stays lit. I know this has nothing to do with the furnace, but I'm wondering if I have a gas delivery issue...
Thanks a lot guys!
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12-10-2016, 04:25 PM
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#11
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Junior Member
Join Date: May 2011
Posts: 16
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With all other appliances shutoff, the furnace still fails to stay lit.
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12-10-2016, 04:52 PM
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#12
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Senior Member
Join Date: Jan 2016
Location: Sarasota
Posts: 587
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Had the same thing happen on my heater a year ago. Comes on for a few seconds then shuts off. Agree with the previous poster - control board not sensing flame so shuts down propane. I replaced both the sensor and control board at the same time so I didn't pick the wrong part and have to pull it out again. Problems solved and has worked fine since then. I also replaced the gasket over the sensor panel, I did not trust the old one to seal after I opened it , they are very fragile. All parts were on Amazon. Good luck.
__________________
2015 Solera 24r
2017 Jeep Wrangler
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12-10-2016, 05:16 PM
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#13
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Junior Member
Join Date: Apr 2016
Posts: 12
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Quote:
Originally Posted by Mcnitchell
Ok, so in experimenting further, I notice when the water heater is lit and actively heating water, if I turn on a stove burner the flame barely stays lit. I know this has nothing to do with the furnace, but I'm wondering if I have a gas delivery issue...
Thanks a lot guys!
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Perhaps the regulator is sticking or needs replacement. I had experienced a similar issue in Spring 2016 with the NT20S furnace on our 2014 camper. After a phone consult with one of the shop techs at our local CW, I learned that the regulator was the culprit. I ordered one for $26 from amazon. After I replaced it problem was solved.
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12-13-2016, 11:39 AM
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#14
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Senior Member
Join Date: Dec 2010
Location: East Berlin
Posts: 734
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Had similar thing happen turned out it was a whip on the propane cylinder that was being used. Changed to different bottle and worked fine. Found bad propane whip replaced no more problem. The bad whip was allowing proper pressure to build up but not the required flow rate of gas.
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12-13-2016, 11:44 AM
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#15
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Pickin', Campin', Mason
Join Date: Aug 2015
Location: South Western PA
Posts: 19,051
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Quote:
Originally Posted by Mcnitchell
Ok, so in experimenting further, I notice when the water heater is lit and actively heating water, if I turn on a stove burner the flame barely stays lit. I know this has nothing to do with the furnace, but I'm wondering if I have a gas delivery issue...
Thanks a lot guys!
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It has everything to do with the furnace!
The furnace burner is one of the largest consumers of propane in your camper.
If the stove barely stays lit, the furnace likely wont either.
__________________
2022 Cedar Creek 345IK 5th Wheel•Solar & Inverter•2017 Ford F-Series SCREW 4x4•Factory Puck•B&W Companion•TST Tire Monitor w/Repeater•Sinemate 3500w Gen.
F&AM Lodge 358 Somerset, PA - JAFFA Shrine - Altoona, PA
Days Camped ☼ '19=118 ☼ '20=116 ☼ '21=123 ☼ '22=134 ☼ '23=118☼ '24=64
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12-13-2016, 11:49 AM
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#16
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Junior Member
Join Date: May 2011
Posts: 16
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I ordered a new regulator and a new whip. I noticed one of my two whips would leak when handled, but did not appear to leak when sitting stationary. If this doesn't work, I'll dig into the furnace itself.
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12-13-2016, 12:04 PM
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#17
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Junior Member
Join Date: Apr 2016
Posts: 12
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Propane supply to furnace issues
Quote:
Originally Posted by Mcnitchell
I ordered a new regulator and a new whip. I noticed one of my two whips would leak when handled, but did not appear to leak when sitting stationary. If this doesn't work, I'll dig into the furnace itself.
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The clue to the tech that my regulator was at fault was that, if burners on the stove were burning when the ignitor attempted to light the furnace, was that the burners would go out. Did you try that test yet?
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12-15-2016, 10:50 AM
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#18
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Junior Member
Join Date: May 2011
Posts: 16
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Fixed! Installed a new regulator and that did it. What a difference it made as well.
Thanks for all your help andesk suggestions!
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