Suburban furnace on 2015 21BD

JDZO6C5 · 01-18-2016, 07:48 PM

Hello everyone,

I purchased my hybrid in April 2015 and since then, I have had quite a bit of problems so far. The only issue that has not been resolved up to now is the furnace. Since I purchased this camper the furnace never ignited when I was just on the battery alone. When I was hooked up to my generator or to my house it worked as normal. I have called multiple times to the dealer and taken it in once for the furnace issue. I always get the answer that my battery needs to be fully charged at 12.6 volts. So they give me back the camper without doing much of any troubleshooting. I now have three brand new batteries and every battery is fully charged and the furnace will not ignite with any of the three. It will only start the fan process, but the pilot/burner will not ignite. So today, after three months of putting this issue to the side since it's winter. I got motivated and decided to check this furnace out myself. I put one of my batteries in and hooked it up. Before I hooked it up, I got a multimeter and checked the voltage. The meter read it was 100% charged, more than enough to spin that blower fan and close the sail switch to ignite. I turned on the thermostat and it did the usual thing. The fan would turn on for a few minutes and just stop with no fire. So I decided to take off the wood cabinet panel to access the furnace and of course there it is, with the back of the furnace facing me of course. I then took off the furnace's back panel from it. There I can see the burner/pilot and etc.
I decided then to switch the thermostat on and see if that would make a difference. What do you know! It ignited. I tested it several times with the panel on and the panel off and got the same result. It would ignite with the panel off, but not ignite when I placed the panel back on. So my next thought was relief that I'm not crazy, and the whole battery explanation I got from the dealer and others was incorrect. So my thought is that the furnace will have to pull in air or there is a vacuum tube that produces negative vacuum, so that the sail switch can close. Im thinking there isn't enough air going through in order to close that sail switch. I just don't know at this point if there is some adjustment that can be made or if I need to replace something, such as the sail switch or drill some holes on that back panel, which probably isn't a great idea. I am at high altitude, which could be a factor, but I shouldn't have to take off the cabinet panel and furnace panel in order for it to ignite with just the battery. So I just was curious if anyone has had the same issue? Any suggestions or solutions would be helpful. Thanks.

rbq · 01-18-2016, 10:17 PM

The exhaust vent for this furnace should have 2 parts. One part to exhaust & the other part to draw in outside air for combustion. Are they both clean? Another thought is that when I had my PUP I used to have the same problem of the furnace not igniting properly. My brother opened up the case & put a stiff piece of electrical tape on the sail switch to make it bigger. It worked fine after that. Might want to see about increasing size of sail switch with some tape.

RACarvalho · 01-18-2016, 10:21 PM

I dont believe it's a question of air flow for in this case it would not work with external power too...
Is it possible that this panel that you are taking off is somehow shorting the battery 12v conection to the igniter so it doesnt ignite?

JDZO6C5 · 01-19-2016, 10:09 PM

Quote:

Originally Posted by rbq

The exhaust vent for this furnace should have 2 parts. One part to exhaust & the other part to draw in outside air for combustion. Are they both clean? Another thought is that when I had my PUP I used to have the same problem of the furnace not igniting properly. My brother opened up the case & put a stiff piece of electrical tape on the sail switch to make it bigger. It worked fine after that. Might want to see about increasing size of sail switch with some tape.

Yes, I need to check the intake and exhaust ports on the outside for anything blocking the air flow. However, I don't understand why the furnace ignites when hooked up to shore power or my generator. I would think if the problem was an air flow issue that it wouldn't work even hooked up to a 120 outlet unless if hooked up to shore power, it will bypass the sail switch and just ignite? Where as on a 12 volt battery it needs the sail switch? Doesn't sound right to me.

JDZO6C5 · 01-19-2016, 10:16 PM

Quote:

Originally Posted by RACarvalho

I dont believe it's a question of air flow for in this case it would not work with external power too...
Is it possible that this panel that you are taking off is somehow shorting the battery 12v conection to the igniter so it doesnt ignite?

I don't think so. If I leave the furnace back-panel on, but leave one side loose by not tightening the screw all the way, which by doing this, leaves a very small gap on that side. The furnace will ignite. It pulls in that little bit more of air through that gap that will allow it to ignite and work as normal, but if I completely tighten it, it will not work. It's lacking that additional air vacuum. There are two air ducts that connect to the back sides, one on each side. They're oval foil tubes just like a dryer, which they travel opposite directions from the furnace to the air duct holes that bring the hot air into the camper to warm. Those don't appear to be an issue. They don't have any obstruction from what I can see in them. I don't think it would cause my issue anyway if they were obstructed, since air is getting pushed out of those oval ducts and not pulling in. The furnace is igniting because air is being pulled more into the furnace by taking off that rear furnace panel off.

**Bama Rambler** · 01-20-2016, 08:27 AM

I'd say that you're right on the verge of too little air flow across the sail switch and leaving a small gap in the housing allows enough flow to close it.

The difference between being plugged in and being on battery is that on battery, you have about 12.6 volts and when plugged in the converter is putting out about 13.8 volts and that probably spins the fan just enough faster to close the sail switch.

Check for obstructions in the burner side of the unit as well as in the occupant side of the unit.

TURBS · 01-20-2016, 09:57 AM

Quote:

Originally Posted by Bama Rambler

I'd say that you're right on the verge of too little air flow across the sail switch and leaving a small gap in the housing allows enough flow to close it.

The difference between being plugged in and being on battery is that on battery, you have about 12.6 volts and when plugged in the converter is putting out about 13.8 volts and that probably spins the fan just enough faster to close the sail switch.

Check for obstructions in the burner side of the unit as well as in the occupant side of the unit.

I agree!

Op, where is the furnace cold air return?
I've not seen you mention it.
I've seen where they cut small slits in a cabinet face and in your case maybe they are not big enough or there's not enough slits to provide enough air flow.

2015 Columbus 320RS
2008 2500HD Duramax
2015 nights camped "34"

JDZO6C5 · 01-20-2016, 12:13 PM

I agree with you. The problem is my battery at 100% charge only reads 13.4 volts on the meter. Any where from 12.6 and up is considered full charged. The sail switch should close with the blower even if the battery is not 100% charged. The blower will start at a volt level as low as 10.5 volts(of course at that level you can have mixed results). My point is my battery will never be at 13.8 and it shouldn't have to be either in order for that blower to close the sail switch. Plus, since the converter will max out at 13.8 volts when plugged in to my house the battery will never fully charge at 100% when plugged in and using the camper converter to charge the battery. It would only charge up to 70-80% based on the limitation of the converter itself. My battery will only charge to 13.4 volts if it's hooked to my trickle charger in my garage. Also I have camped with lots of people with a battery that's at 11 plus volts and their furnace ignited with no problems.

JDZO6C5 · 01-20-2016, 12:18 PM

That's a great question! I can only assume that the air return is the wood cabinet panel I took off to access the back of the furnace. That panel is vented, but looks nothing like your picture. Every air return vent I've seen has been located to the side of the furnace and not behind.

TURBS · 01-20-2016, 12:21 PM

Look inside the cabinets on either side of furnace for a grill or lack there of.

2015 Columbus 320RS
2008 2500HD Duramax
2015 nights camped "34"

bob caldwell · 01-20-2016, 05:56 PM

Mine is behind

JDZO6C5 · 01-20-2016, 10:48 PM

Quote:

Originally Posted by TURBS

Look inside the cabinets on either side of furnace for a grill or lack there of.

2015 Columbus 320RS
2008 2500HD Duramax
2015 nights camped "34"

The wood cabinet panel that is directly behind the furnace is the grate or air vent. There is no other vent inside the cabinet. I confirmed this with Forest River. They were not very much help with my situation. They of course told me to contact Suburban, which I wasn't successful in doing.

JDZO6C5 · 01-20-2016, 10:58 PM

Im going to check the intake and exhaust ports on the outside to see if there is any obstruction of air flow, but I am just contemplating the thought of just replacing the sail switch to see if that does anything. I don't really want to, since that requires pulling the entire furnace out, but obviously that may have to be my next step anyway if the intake and exhaust ports are not obstructed.

TURBS · 01-21-2016, 08:00 AM

So the intake is inside a cabinet? Is there another intake from the cabinet to to camper?
Or is it just trying to suck air from the cabinet?

2015 Columbus 320RS
2008 2500HD Duramax
2015 nights camped "34"

Filthy Beast · 01-21-2016, 08:43 AM

Quote:

Originally Posted by rbq

The exhaust vent for this furnace should have 2 parts. One part to exhaust & the other part to draw in outside air for combustion. Are they both clean? Another thought is that when I had my PUP I used to have the same problem of the furnace not igniting properly. My brother opened up the case & put a stiff piece of electrical tape on the sail switch to make it bigger. It worked fine after that. Might want to see about increasing size of sail switch with some tape.

Not trying to hijack this thread, but, if you had to add to the sail switch to make this furnace work, you are not flowing enough air either. This would increase the exhaust temps and possibly overheating of the unit.

TURBS · 01-21-2016, 09:28 AM

Quote:

Originally Posted by Filthy Beast

Not trying to hijack this thread, but, if you had to add to the sail switch to make this furnace work, you are not flowing enough air either. This would increase the exhaust temps and possibly overheating of the unit.

Agreed!

Could be a restriction on the heated air side to the registers.

2015 Columbus 320RS
2008 2500HD Duramax
2015 nights camped "34"

**Bama Rambler** · 01-21-2016, 09:51 AM

Quote:

Originally Posted by JDZO6C5

I agree with you. The problem is my battery at 100% charge only reads 13.4 volts on the meter. Any where from 12.6 and up is considered full charged. The sail switch should close with the blower even if the battery is not 100% charged...

I 100% agree. My point was to indicate that there is a problem with the furnace that needs to be rectified. Sorry I wasn't very clear about that.

Quote:

Originally Posted by JDZO6C5

...My point is my battery will never be at 13.8 and it shouldn't have to be either in order for that blower to close the sail switch.

We agree on this. There's definitely something wrong. My guess is an obstruction, but it could be something else.

pkenley · 01-22-2016, 12:59 PM

JDZO6C5 After spending one fall in Silverton Co without furnace working, This last fall I was thinking it was an altitude issue as well.(worked in Dorango on shore power), . so I too pull the cover off as you did and it worked fine. Spent 4 weeks in comfort. Today, back home, I put the cover on and it works but I;m on shore power now so I might go back out and pull the plug and see if it works.

hillsdaletc · 01-22-2016, 07:27 PM

Have seen a few of these. You need to install one more duct. Your furnace is pushing more air flow than your duct work can handle. This loads the blower motor and causes it to draw more ampherage. As mentioned earlier the converter puts out a strong supply of amps to fully power the double blower wheels.
Too little air flow will also cause the temp. Limit switch on the furnace to kick out and shut down the furnace.
You need another duct.

pkenley · 01-22-2016, 08:38 PM

Quote:

Originally Posted by hillsdaletc

Have seen a few of these. You need to install one more duct. Your furnace is pushing more air flow than your duct work can handle. This loads the blower motor and causes it to draw more ampherage. As mentioned earlier the converter puts out a strong supply of amps to fully power the double blower wheels.
Too little air flow will also cause the temp. Limit switch on the furnace to kick out and shut down the furnace.
You need another duct.

and this will solve the issue when it's only a problem at high altitude??

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