Journey with Confidence RV GPS App RV Trip Planner RV LIFE Campground Reviews RV Maintenance Take a Speed Test Free 7 Day Trial ×


Reply
 
Thread Tools Display Modes
Old 12-10-2016, 10:23 AM   #1
Junior Member
 
Join Date: May 2011
Posts: 16
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!
Mcnitchell is offline   Reply With Quote
Old 12-10-2016, 11:14 AM   #2
Site Team
 
Mr. Dan's Avatar
 
Join Date: Mar 2014
Location: Grayson County, Texas
Posts: 21,473
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
Mr. Dan is offline   Reply With Quote
Old 12-10-2016, 11:17 AM   #3
Junior Member
 
Join Date: May 2011
Posts: 16
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.
Mcnitchell is offline   Reply With Quote
Old 12-10-2016, 11:22 AM   #4
Site Team
 
Mr. Dan's Avatar
 
Join Date: Mar 2014
Location: Grayson County, Texas
Posts: 21,473
Quote:
Originally Posted by Mcnitchell View Post
....
And I don't want to just start ordering parts.
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
Mr. Dan is offline   Reply With Quote
Old 12-10-2016, 12:14 PM   #5
Junior Member
 
Join Date: May 2011
Posts: 16
Standing by. :-)
Mcnitchell is offline   Reply With Quote
Old 12-10-2016, 01:19 PM   #6
Member
 
Join Date: Oct 2015
Posts: 52
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.
Cardinal5er is offline   Reply With Quote
Old 12-10-2016, 01:47 PM   #7
RVdoctor
 
Join Date: Jun 2016
Location: South Dakota
Posts: 77
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.
rvdoctor is offline   Reply With Quote
Old 12-10-2016, 01:49 PM   #8
Senior Member
 
Join Date: Feb 2016
Location: NJ
Posts: 606
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
DrLewie is offline   Reply With Quote
Old 12-10-2016, 02:20 PM   #9
Senior Member
 
TimVWulp's Avatar
 
Join Date: Jan 2015
Location: West Michigan
Posts: 641
Quote:
Originally Posted by Mcnitchell View Post
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!
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
TimVWulp is offline   Reply With Quote
Old 12-10-2016, 03:08 PM   #10
Junior Member
 
Join Date: May 2011
Posts: 16
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!
Mcnitchell is offline   Reply With Quote
Old 12-10-2016, 04:25 PM   #11
Junior Member
 
Join Date: May 2011
Posts: 16
With all other appliances shutoff, the furnace still fails to stay lit.
Mcnitchell is offline   Reply With Quote
Old 12-10-2016, 04:52 PM   #12
Senior Member
 
Rich.M's Avatar
 
Join Date: Jan 2016
Location: Sarasota
Posts: 587
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
Rich.M is offline   Reply With Quote
Old 12-10-2016, 05:16 PM   #13
Junior Member
 
Join Date: Apr 2016
Posts: 12
Quote:
Originally Posted by Mcnitchell View Post
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!
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.
Fuzzy53 is offline   Reply With Quote
Old 12-13-2016, 11:39 AM   #14
Senior Member
 
Join Date: Dec 2010
Location: East Berlin
Posts: 734
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.
Rich5117 is offline   Reply With Quote
Old 12-13-2016, 11:44 AM   #15
Pickin', Campin', Mason
 
5picker's Avatar
 
Join Date: Aug 2015
Location: South Western PA
Posts: 19,051
Quote:
Originally Posted by Mcnitchell View Post
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!
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
5picker is offline   Reply With Quote
Old 12-13-2016, 11:49 AM   #16
Junior Member
 
Join Date: May 2011
Posts: 16
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.
Mcnitchell is offline   Reply With Quote
Old 12-13-2016, 12:04 PM   #17
Junior Member
 
Join Date: Apr 2016
Posts: 12
Propane supply to furnace issues

Quote:
Originally Posted by Mcnitchell View Post
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.
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?
Fuzzy53 is offline   Reply With Quote
Old 12-15-2016, 10:50 AM   #18
Junior Member
 
Join Date: May 2011
Posts: 16
Fixed! Installed a new regulator and that did it. What a difference it made as well.

Thanks for all your help andesk suggestions!
Mcnitchell is offline   Reply With Quote
Reply

Tags
furnace, suburban

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Featured Campgrounds

Reviews provided by

Disclaimer:

This website is not affiliated with or endorsed by Forest River, Inc. or any of its affiliates. This is an independent, unofficial site.



All times are GMT -5. The time now is 10:54 PM.