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Old 01-06-2012, 01:24 PM   #1
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Repairing our Suburban SF-30 - the Agony w/o the Ecstasy

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.
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Old 02-02-2013, 10:47 PM   #2
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Great Post, I have a motor thats seems to be going bad. When you did your extraction of the unit. If you recall what did it look like to replace the motor. appreciate that i have your guide to go by
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Old 02-05-2013, 09:55 AM   #3
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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, 10:34 AM   #4
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Sorry about that, they are expensive to replace and they shouldnt be. Not sure what mine is doing making a slight vibrating sound for a half a second when it shuts off. looked it over. will wait and see hope yours works out.
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Old 02-05-2013, 10:45 AM   #5
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More on the POS Surburban SF-30

I think mine has a similar noise issue with the squirrel cage blower, so PLEASE let me know what you figure out... I have put this off, just because I don't wanna deal with it. I do know from my experience that the tear down of this unit is a bear.

You can probably bench test the electronics yourself, however, fairly easily, but it might be worth taking to a shop if you are not handy. (not the one i used however).

Here is the service manual online:

http://manuals.heartlandowners.org/m...e_Suburban.pdf
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Old 10-31-2014, 07:46 PM   #6
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Wow, what a story. I have a 12,000 BTU suburban furnace that won't light inside my 1994 Ford Coachman class B RV. I employed your brilliant cleaning technique and sniff test (smell propane), but still won't light. Installation crummy same as yours. Have to cut wire, no gas shut off. I bought a gas plug in case I decide to remove the unit for repairs or replacement. Back in the day, I never thought about having heat in an RV, but once I got used to it, I'm spoiled. Oh, I don't think Suburban makes the 12,000 unit.. I can't seem to find one on line.. cursory check. I'll keep looking, cause if it's a minor part, it might be best to buy a whole new unit than go thru hell you did.
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Old 10-31-2014, 07:54 PM   #7
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Ummm not to start an argument but the unit was a 2005? It's 2014 right? First maintenance ever? 14 years of trouble free service seems like it did pretty good.


Life is a highway!!!!!
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Old 10-31-2014, 07:54 PM   #8
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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 10-31-2014, 08:10 PM   #9
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walk the walk,

Reading your first post was almost spooky for me. I went through that exact troubleshooting and dismantling process last fall with my Suburban furnace. I was laughing out loud (sorry) at some of your descriptions of how frustrating it is to find out how shoddy things like this are put together in our RVs. Mine was exactly the same. I too was stunned that you had to cut wires just to gain access to this sorry excuse of an appliance. Same with the gas hook-up. In the end, just like you, I got mine working. The good news is you (and me) know more about these furnaces than most now. I always try and fix things like this myself first before going to the repair shop. One, to gain knowledge about the particular problem unit, and two, to save money. Its a bonus when it works out in the end. Good job.
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Old 12-27-2014, 08:32 PM   #10
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SF-30

Pulled mine out the other day. Stopped working last year. For a while it would work once in a while. Then after a while it would no longer spark. I am confidant that I can repair it. I'm not paying $600 for a new one. I have a 2006 Montana Mountaineer 29RLS. It was not too difficult to remove. Same shoddy installation though, I think they are all put together like that. I have to fix before I leave for Fla. in March. I will report back on what I find.
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