Maintain Suburban Furnace

pokgunner · 08-17-2015, 09:37 PM

I have a suburban furnace in a 2010 Suncrusier (Adventurer). After completing a long Alaska/Yukon trip, it will not light. The fan comes on, no heat, and then shortly shuts off. I am 90% sure that the burner area is dirty, since the exhaust pate was is caked with dust/dirt. But I can not figure out how to get to the burner area. HELP

Where the intake exhaust is there is a plate held by 6 screws, but it will not come off, easily. This plate is screwed to a panel that holds the license plate. But it will not come off, because of the exhaust plate. I do not want to muscle the plate off without knowing that is what is required. But by prying the panel to look behind it does not appear that I would get to the burner anyway.

The furnace appears to be below the floor, but the gas line that feeds goes in to the bottom part of the flooring and then where I have not a clue. I tore as much as I thought reasonable from under the bed, saw no access to the furnace and it is on the wrong side anyway.

The furnace is wrapped with insulation.

Would removing the exhaust plate and panel get me to the burner? If so is there a trick to removing the exhaust plate or do I jut muscle it off?

If I can not get to the burner by removing the exhaust plate, do I have to remove the whole furnace, or is there some small portion of the insulation I can remove to to clean the burner?

Gormleys · 08-19-2015, 04:14 PM

Wow! Sorry for your troubles. I don't have any answers for you but wanted to bump up this stream so that it doesn't get lost. Hopefully someone more familiar will respond. If not, also try adding your discussion to the "RV SYSTEMS AND APPLIANCES" forum here under the "RV Forums" pull-down.

Good luck!

andy29847 · 08-19-2015, 05:15 PM

Soot around the burner holes is most likely your problem. Use the furnace exhaust ports to blow the soot out of furnace with air. You can use an air compressor or possibly a yard blower.

grtharris · 08-19-2015, 08:44 PM

pokgunner you will have to remove the furnace, the burner is removed from the bottom of the furnace. You will need to remove the large plate to gain access. The combustion air and exhaust pipes are friction fit and require a bit of working to get them to slide apart. Here is a good video.

https://www.youtube.com/watch?v=ayRyCjvPskQ

pokgunner · 08-26-2015, 10:11 AM

Thanks everyone I am still traveling and have not had internet access. I managed to get the intake/exhaust pipe off, but juts muscling it (bent the Plate a little bit). The video helped. But now I have another question/problem.

After I removed the the access plate to the furnace, I fund that about 6 inches of the weather stripping they used to seal the plate had dropped prior to installing the plate. That plus my Alaska trip resulted in about 1/2 of the cavern that the furnace sits in. I do not think this caused the problem as I do not see how that dirt could get to the burner chamber.

But I would like to clean it all out. And prevent it from happening again. It appears to me that the furnace sucks in air from the floor vent above it and then pushes the heated air to the other floor vents. That is there is no air passages shared with the heat pump. Is that correct? I want to use an air hose to blow all the dirt out but do not want to push it back into someplace else if the cavern goes some where.

Is there a need for such a large cavern? I ask because I am not convinced that the gap I found is the only place dirt entered, but I can not see the whole cavern. I am highly tempted to use some sheet metal to reduce the size of the cavern, so I can be sure it is sealed. But I worry about unintended consequences. Any thought?

grtharris · 08-26-2015, 03:13 PM

pokgunner You are correct the furnace plenum is not shared with the AC/Heat pump. I would pull the furnace, which you have to do to get to the burner, and blow air in the floor vents one at a time covering the other ones working from the front to the rear.
The air for the burner comes through the intake pipe.
After you get all of the dust out, put it back together making sure all of the seal are in place. attached are a couple of pictures. The black and white drawing is your coach. The color one is a later year but still the same.
Don't know about reducing the size of the furnace enclosure.

shiggs68 · 08-26-2015, 05:25 PM

Quote:

Originally Posted by pokgunner

Thanks everyone I am still traveling and have not had internet access. I managed to get the intake/exhaust pipe off, but juts muscling it (bent the Plate a little bit). The video helped. But now I have another question/problem.

After I removed the the access plate to the furnace, I fund that about 6 inches of the weather stripping they used to seal the plate had dropped prior to installing the plate. That plus my Alaska trip resulted in about 1/2 of the cavern that the furnace sits in. I do not think this caused the problem as I do not see how that dirt could get to the burner chamber.

But I would like to clean it all out. And prevent it from happening again. It appears to me that the furnace sucks in air from the floor vent above it and then pushes the heated air to the other floor vents. That is there is no air passages shared with the heat pump. Is that correct? I want to use an air hose to blow all the dirt out but do not want to push it back into someplace else if the cavern goes some where.

Is there a need for such a large cavern? I ask because I am not convinced that the gap I found is the only place dirt entered, but I can not see the whole cavern. I am highly tempted to use some sheet metal to reduce the size of the cavern, so I can be sure it is sealed. But I worry about unintended consequences. Any thought?

Continue your burner cleaning effort. However that is not your original problem. Here is the correct sequence of operation.

When heat is called for, the blower starts.
The circuit board detects the blower is upto speed by the sail switch.
The circuit board then turns on the gas and igniter.
If the burner does not fire, the logic turns off the gas and leaves the blower on to ensure the unburnt gas is purged. The thermostat will need to be moved to hot then back to reset the sequence.

If the speed is not sensed by the sail switch, the blower turn off (your symptom). Speed is controlled by low battery voltage or bad or stuck sail switch.

If you are unclear on my description, the service manual for your Suburban furnace are online and show my description in a flow chart form.
http://www.bdub.net/manuals/Suburban_Service_Manual.pdf

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TravellingRVDoctor, LLC

Hikerdogs · 08-27-2015, 07:42 AM

Another thing to check is the electronic igniter. We had a similar problem after returning from our first Alaska trip in 2007. After traveling hundreds of miles on dirt and gravel roads the entire furnace and surrounding area was covered with dirt and grime. Once the furnace was removed it was obvious the igniter was also covered with crud and couldn't transmit a spark. A thorough cleanup and everything worked fine.

Just a couple notes. I used a vacuum to clean the ducts and furnace, and the surrounding area. The registers are held in with a couple screws and can easily be removed. It's not nearly as messy as pushing all the dirt around with air.

The other thing is that looking back the failed igniter should have obvious. Previously when the furnace started I could hear the snap, snap, snap of the igniter attempting to fire up the furnace. When it didn't start I didn't even notice the sound was missing. After cleaning it the sound returned and the furnace worked properly.

dezrtracr · 08-27-2015, 12:13 PM

I had the same problem. First time out with the new MH and the Suburban furnance was working fine. During the night, the furnance quit working. It would start, run for a short period, then shut off. The dealer ended up replacing the main circuit board and that resolved the problem.

pokgunner · 08-27-2015, 06:40 PM

Thanks to all. My problem was simply dirt, the sail switch was not an issue. I do not think it is possible to describe how much dirt got in the system and still be believable. In all it was way more than a couple of pounds.

The suggestion of sealing all the floor vents and blowing from front to back, is a great one that I would not have thought about.

I suspect that most of the problem was due to the gap in the foam seal, but a lot just came in the intake port. (on four occasions the license plate was unreadable, prior to washing). If I ever take another trip like that again, and I plan on it, I am going to devise some kind of cover for the intake/exhaust tubes while traveling on dirt and or mud.

Again thanks to all. especially grtharris. I do not know where or how you got the drawings, If I did I never would have used this site.

grtharris · 08-27-2015, 07:50 PM

pokgunner, For future reference they are on the Winnebago web site. Here is a link to get started with.
Winnebago Industries
The electrical and plumbing diagrams are 2D and the parts catalog are 3D for 2011 and newer. You have to load some software and do a little tweaking to get the 3D to work. Also on the parts catalog page is the service parts list which will show all of the parts used to build your coach. Lots of good stuff.