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Old 01-06-2012, 01:24 PM   #1
Join Date: Mar 2008
Location: Little Rock
Posts: 91
Repairing our suburban sf-30 furnace

Our 05 Wildwood came with an under-the-range mounted Suburban SF-30 propane furnace, which worked fine when we bought our trailer second hand in early 2008 -and has worked fine since until recently. Lately, it has either been hard to get started (taking several tries to get the burner to ignite), or like now, won't start at all and fails after 3 tries to ignite (our SF-30 has a 3 try controller). So, with cold temps and no heat at all, I set about learning all I could about this unit, in an effort to try to fix it myself if possible.

Part of the reason I went DIY on this is the local dealer wants $100 just to bench test the unit, and NO ONE wants to do remote service anymore.

So, armed with my vast troubleshooting knowledge and electronics background, I started off to do the deed myself. First, I downloaded every manual on the Suburban furnaces (and in particular the SF-30) that I could get my hands on, and poured over them. I tried every test I could WITHOUT removing the unit, but in my case, the sail switch and limit switch is working, and the unit is TRYING to fire off, but fails after 3 tries and locks out, which narrows down the number of things that can actually be wrong with it.

One test that is not documented anywhere is this one which I came to on my own: you can check to see if the gas valve is operational by putting the unit in heat mode and standing outside by the exhaust port while it tries to ignite. You will hear the unit attempt to fire off 3 times (the ignitor tries to spark several times during each round), and you can SMELL propane in the exhaust when the ignition fails if the gas valve is opening. This helps to rule out the limit switch, the sail switch, the gas valve, etc, but not the controller board or the ignitor, or a dirty combustion chamber.

The Suburban manuals makes removal and cleaning of the SF-30 SOUND EASY. IT IS NOT! In fact, given the shoddy install job done by Forest River installers at the factory, it is made harder than it should be.

FOR EXAMPLE, there is NO GAS SHUTOFF VALVE at the furnace. So, you have to shut off the gas at the tank, with the stove top burner going to burn off the excess propane in the line, BEFORE you disconnect the propane fitting. You also have to disconnect BOTH electric and battery power and work by flashlight to reduce the risk of spark/explosion.

The whole furnace unit is suspended in the cabinet frame with only two cabinet screws holding it in place (incredible!) and sits on top of two small blocks of wood, loosely attached to the floor, with a small piece of duct insulation filling in the gap. The whole furnace just sits in there loose. I was pretty stunned at the extremely poor quality of the installation of this vital piece of gear when I saw it!

Worse, FR provides no outside access door either (although FR could spend a few bucks extra and purchase the SF-30F model and install a door if they wanted to do a QUALITY job!) So, there is ZERO access to the on/off switch on the rear of the unit, or to the controller board, or to the blower motor, etc., without removing the ENTIRE furnace.

Also, FR did not install a plug connector for the 4 wires feeding the unit, nor is there enough slack in the wires, and since I am not a midget and I could not reach the factory wire nuts, I had to cut the wires, even though I would have PREFERRED NOT TO do so. A 4 wire connector plug would cost $2 maybe? Why FR opts to install this furnace without one is a mystery to me, but tells me that THERE ARE NO QUALITY AUDITORS WORKING AT THE FR FACTORY... none of this would pass a decent quality audit - I know I am a quality auditor.

The Suburban instructions tell you that the combustion chamber of their furnace needs to be cleaned every year. They do not tell you how TRULY DIFFICULT it is to do this. To get to the combustion chamber, doing it the way they describe, not only do you have to REMOVE THE ENTIRE FURNACE, (which means removing the exterior vent caps and gasket first and its 6 screws), then you have to remove the furnace from its housing (4 screws), remove the blower motor impeller assembly (many many screws), remove the blower motor itself, unscrew the connector to the ignitor at the gas valve, then remove the ignitor assembly and gasket from the combustion chamber (another 9 screws and a nut have to come off just for that step alone), which means dislodging the glob of firewall putty that is factory installed, too. Then you go rent or borrow an air compressor to clean out the labyrinthic combustion chamber. DOES THIS SOUND LIKE SOMETHING YOU WANT TO TO ANNUALLY???

Fortunately, there is an easier way - you can just remove the exterior vent cap and attach the hose from a 12 amp household vacuum cleaner to the exhaust port (it is a perfect fit by the way), and hold your hand over the INTAKE port and every spec of dirt in the combustion chamber will come out, WITHOUT REMOVING THE UNIT, or risking damage to it by completely dissembling it.

In my case, about a 1/2 tablespoon of very fine soot/sand (we live in Florida) came out of the chamber, which is not bad, considering that the furnace was like brand new when we bought it and we have used it maybe 10-15 times over a 4 year period.

Finally, I have learned from a Suburban authorized repair center rep, that given my symptoms, the odds are that my control board has gone bad and is not putting out enough spark. He told me that 9 out of 10 times this is the cause when it will try to ignite 3 times, but not fire off. He says the neon device on the OEM board goes bad often, for whatever reason.

The good folks at Dinosaur Electronics agree. They make an aftermarket control board for this unit called the FAN 50 PLUS PINS, which is a superior replacement to the POS Suburban board.

Given that I can buy the higher quality Dinosaur board for about $100 online, and the OEM board is $139, this is a real no brainer... I can get a better board and install it myself for the cost of putting my furnace on the bench at the local shop.

In conclusion, I think the whole problem here is that Suburban is making a furnace with substandard parts that is being installed in a substandard manner by Forest River, so that it lasts about 3-4 years if you are lucky, and then you have to start removing it and troubleshooting it to fix it. Because of the poor quality install job and the lack of an access panel, troubleshooting it 10 times more difficult than it has to be - and you are put at the mercy of the local dealer to repair the unit yourself. Most of this would not be necessary if both Suburban and Forest River would spend an extra $10 on the furnace and the installation of same. For starters, a gas shutoff valve at the unit seems like a basic safety item. Also, I don't see how this furnace could meet UL standards AFTER the installation if the ON/OFF switch is buried at the back of the unit!!! Lastly, the aforementioned four pin connector seems a must-have given that the furnace needs to be serviced now and then. Either that or just put in an access door! Seriously!

Since I know that a new SF-30 furnace costs about $595, it really makes you wonder where you reach the point of diminishing returns of one's efforts at repairing any furnace like this one. We're having family budget issues like most folks, so I don't have the luxury of buying a new replacementfurnace, or I would... because it would be 100 times easier to just drop a new SF-30 in the cabinet than to go thru this process again. And, if I had taken it into a local shop after removing it myself, the minimum repair bill for replacing a controller board would be about $300. Argh!

Hope this info helps others. At least the vacuum cleaner trick should.
walk_the_walk is offline  
Old 02-05-2013, 09:55 AM   #2
Join Date: Mar 2008
Location: Little Rock
Posts: 91
It's not really any better now...

I have continued to have problems with the furnace... removed it and took it in and had it bench-tested at a local RV shop. It was $70 or so. Nothing wrong with it they said. Installed automotive connectors on all 4 wires to make the reinstall and any future troubleshooting easier. This is something that should be done at the factory. It requires 4 plug-style crimp connectors, 2 of each size, since there are two 24 ga. wires and two 14 gauge wires. You can get these at any auto parts store.

Turned out our problem was low gas pressure from the Marshall Gas Products dual regulator. There is a plastic wrench knob adjustment on the back, so I turned it until the furnace would fire up. Sitting out in the weather must have caused it to be out of adjustment over time, as the gas stove worked fine and no air in the line. Furnace fired up several times with no problem, but made a squeaking noise that we ignored, which we can only attribute to the bench testing.

Now, the squeaking (squealing noise is almost intolerable. It begins at blower start up and comes back when the Tstat is satisfied and the blower slows down.

So, taking this POS furnace in for troubleshooting solved nothing; cost me money; and now it works worse than it did before.

We did discover that you can remove the panel underneath the refrigerator with two screws and get to the back end of the furnace more easily. Not sure how we missed that before, but you can get your whole head into the cabinet under the frig and see what's going on.

What a horrible design and what shoddy unsafe installation that FR uses for this vital component.
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Old 02-05-2013, 10:45 AM   #3
Join Date: Mar 2008
Location: Little Rock
Posts: 91
More on the POS Surburban SF-30

Here is the service manual online:
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Old 10-31-2014, 06:54 PM   #4
Join Date: Mar 2008
Location: Little Rock
Posts: 91
More on our furnace...

The squeaking noise turned out to be a mal-alignment of the squirrel cage blower by the idiot tech whom I paid $75 to tell me there was nothing wrong with my unit, and in the process, he created a problem by his partial dissassembly. Of course, I cant prove that, but it never squeaked before he touched it.

Anyway, it be working like GANGBUSTERS now ever since I replaced the Marshall Gas dual LP autoswitch and regulator. Here in Florida those dont last but a few years as the regulator references outside air and that means humidity and it fails.

So before you service anything... before you remove any wires and add connectors, before you remove the furnace assembly... check that you have no air in the line by starting up the stove and if you have a regulator that is 3 years old, just buy a new one on Amazon and replace IT instead. That takes five minutes and a crescent wrench. Since they are factory set, you then only need to fire up the stove again to make sure there is no air in the line and then fire up the furnace.

We have never had a soot problem with our furnace, or a venturi problem, or a spark problem. It was always gas pressure all along. Argh. Lesson learned the hard way.
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Old 01-19-2015, 06:24 PM   #5
Join Date: Mar 2008
Location: Little Rock
Posts: 91
As further feedback, we have not had a problem with the Suburban furnace since replacing the dual tank regulator. That said, there was one day that it took several tries to light, even though we have the Dinosaur Electronics board installed, but once again, it seemed to be related to the gas pressure, as the tank that the regulator was "pointed to" was pretty low.

So, in my humble opinion, the majority of the problems with this furnace come from low gas pressure, NOT from lack of spark or electrode problems, especially if it has light duty or low usage. The minority of problems come from letting unqualified Billy Bobs work on your furnace, when there's really nothing wrong with it in the first place.
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Old 02-10-2016, 07:03 PM   #6
Join Date: Mar 2008
Location: Little Rock
Posts: 91
Thumbs up The agony & the ecstasy pt.2 - repairing our suburban sf-30 furnace (again!)

My original post on this topic was quite a popular post the last 3 years and I got some great feedback on this, as many have struggled with Suburban furnaces.

This post is here because the problems we thought we were having with our SF-30 not firing up were not resolved after all. And, by after all, I mean after doing all these things:

1. replacing the electronic controller with the Dinosaur Electronics upgraded version (a great product)
2. Removing the unit multiple times, even installing 12V automotive-style quick disconnects on the four main wires. At one point, out of desperation, we even took our furnace to a local RV shop for repair, only to have it returned as "it works fine for us" - when in fact they had not re-assembled it correctly and it squeaked like mad on the re-install, which required me to re-uninstall it for the umpteenth time and take it apart to find the squeak in the blower motor housing, re-assemble and reinstall.

which led to the Final Solution:
3. We Replaced the original dual pressure gas regulator at the tanks, which increased system gas pressure and improved the performance for a few seasons only. But, at this point, it was working so we THOUGHT the problem was solved.

We were SO WRONG!


This winter season the problems came back to roost again. Same symptoms, same problem. The burner would try to light, go tick-tick-tick, you could smell propane being vented out the exterior vent tube, but nothing happened. Maddening.

Based on my lesson learned from last time, I assumed (as I dont own a manometer) that the new Camco dual pressure regulator must have stopped producing the correct gas pressure. I bought another new one on Amazon - a super nice Italian made model with true visual gas level gauges and installed it. $50 and 1 hour later the furnace still would not light. Sigh. That meant that it sure wasnt the gas pressure!

So, I went back to the manuals for a review, as I was dreading the whole neck-straining, back-breaking furnace removal process, and tried to decide what parts to buy in advance so the repair would go quickly and smoothly (HA! -that never happens with a furnace repair!)

I bought a new ignitor w orange cable, a burner gasket and a sail switch - the later just in case, since you have to take it all apart anyway. I studied the manuals to remind myself of how the unit works and comes apart.


This weekend we did the dirty work. It was a super tedious job as everyone who has ever attempted it knows. Bleed off the gas line, remove the cover, remove the inner sheet metal cover and hold-down screws, then go under the fridge to disconnect the wires. Luckily I have the 4 quick disconnects, so this part was easier.

To get to the infamous Suburban electrode to check it with a flashlight LOOKS EASY IN THE MANUAL. It is anything but. Perhaps there is a way to dismantle the entire SF-30 that I am missing, to get to the area where the electrode assembly is located, but on mind, this simple task meant also removing the entire wheel blower motor cover and motor, several wire connectors and more, so that the entire stainless steel gas line and regulator can come loose, then removing the screws on the gasketed plate on the burner assembly where the ignitor lance lives. It was almost like brain surgery with much risk of breaking some part or not being able to figure out how to get it re-assembled.

Tip: we took lots of pics as we disassembled the unit on our workbench (which came in handy later) and used 3 seperate coffee mugs for the different sets of screws, so they did not get mixed up (one for the blower motor assembly, one for the burner gasket cover, etc.). I think I ended up using damn never half the small tools I own, so I hope you have more than just a screw driver and pliers when you attempt this.

Long story short, we finally got to the heart of the beast. We were able to remove the SS gas line assembly and regulator and the burner cover and its gasket (which definitely needed replacing anyway) and could see inside the infamous burner itself. The heart of darkness.

Surprisingly, there was a lot of soot inside there, even though I regularly try to vacuum it out via the outlet tube. I guess my idea is only half effective, as there were at least 2 teaspoons of black silt in the corner inside. But, we did find the problem. AS YOU MIGHT EXPECT, it can best be blamed on POOR QC at the SUBURBAN FACTORY in Tennessee. I have to call them as i see them and the RV dealer never dissembled this unit, as it had the original gasket on it. AND, here's the rub: The tip of the lance was not positioned correctly height-wise, nor horizontally either. It was quite obvious, on seeing this, WHY we have had so much trouble with this furnace since we bought our FR Wildwood from the original owner, who had only used it 6 times (so it was nearly brand new when we got it).

In fact, I did not need the ignitor I bought on Amazon, and returned it unopened. The original factory OEM ignitor was not corroded, it just needed to be bent into the correct position. (For the geeks out there, the tip of the lance as 0.250" above the face of the burner, rather than 0.125" and the tip of the lance was nowhere close to the holes in the burner where the gas comes out, so I am not sure how it ever worked right).

Anyway, replacing the ignitor lance assembly looked like a bear, as it is tightly wound in there and has grommets and such and is a job best avoided if not needed. Instead, we measured carefully and repositioned the ignitor lance, checked the gas orifice to be sure it was not clogged (it was fine), then cleaned up some minor rust on the burner (and learned that all burners likely get this minor rust over time), vacuumed up the black silt, installed the new burner access cover gasket, and then went through the 30 minute process of carefully reinstalling all the parts and pieces and wire connectors, back where they went originally, checking that the dual squirrel cage motor assembly was properly seated so it would not squeak, reattached the wire connectors, re-installed wire tires, and made sure every single OEM screw was back in its original location.

The re-assembly portion of the surgery went well, so with high spirits, we re-installed the SF-30 in our trailer, checking alignment with the internal air distribution duct, hooking up connections, and re-installing/re-caulking the outside vent hole cover and screens with its six screws. This took my wife and I another half hour to do. Wow, was that the job from Hell.

GREAT NEWS! After all this, it worked like a charm. Fired up on the first try! Fired up each and ever time thereafter. No leaks, no issues, no problems. We were nice and toasty warm all weekend long, and it was quite cold this weekend, so this was great!

LESSONS LEARNED: the position of the lance tip inside the burner can be very critical if your furnace will try to start, but not start, and you can hear the tick-tck-tick and smell the gas valve opening and can smell the propane. You have no spark and the lance tip of the ignitor creates that spark. If it is not the pressure from the regulator or a low tank, then you could end up needing the same repair.

And, this repair is not for the faint of heart. I recommend it only to appliance repair techs, propane techs, mechanical or electrical or robotic engineering graduates or Stephen Hawking. Everyone else should steer clear. This is not a user servicable item, really.

I say that as if you were to, for example, not buy a new gasket and try to get by on the cheap and reuse the original gasket, and if it leaked you would never see it, but you could be exposed to carbon monoxide inside your trailer. (Of course, we have a new CO sensor mounted at floor level within 2 feet of our unit, but I am not sure if this is standard for all RVs.)

Still, if yours is broken, and you have good tools and you have lots of time and patience and want to save the $120 you will probably have to pay, it is possible to do this job. It's just anything but easy or fun. Satisfying when its done and done right, though.

Its a shame that Suburban did not do a recall of the 2004-2005 SF-30s as might was clearly not set up at the factory, and since its installed as a unit, I dont see this as a FR screw up. This is all on Suburban.

While we had it apart, I snapped a few pictures of the burner, lance and probe, as the one in the Suburban manual is pretty useless and hard to interpret.Hope this helps someone else, even if just to decide to take the unit to the shop.

Pictures shows the dissembled SF-30 facing with the burner cover open, with the old gasket still attached. A 2nd pic shows the venturi that feeds the burner - it looks like a miniature space shuttle nozzle. A 3rd shows the actual lance itself, the tip of which is directly over the burner, which lies underneath the cover that is open. A 4th shows the stainless steel gas orifice and cover (the orifice looks like a brass pencil eraser).

Pretty amazing device really, and once the lance is set to 1/8" instead of 1/4" and is positioned as shown over the holes of the burner, it fires like clockwork! I expect that this will finally end all of our SF-30 troubles and we saved hundreds by not having to buy a NEW unit when there was nothing wrong with ours but an adjustment.
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