Home » Public Forums » GMCnet » Need Help With Suburban Furnace Adjustment
| Need Help With Suburban Furnace Adjustment [message #104907] |
Wed, 03 November 2010 08:54  |
pistolnut
Messages: 19
Registered: September 2010
Location: Caldwell, TX
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My '76 Birchaven by Coachmen has what appears to be the original Suburban furnace. The unit works, however it produces very noticable vapor/smoke from the exhaust port and the screen on the port has a lot of soot buildup. My manual gives the procedure for adjusting the air and therfore the flame on a different brand of furnace, can anyone tell me how to do so with the Suburban? The unit works well otherwise, I think its just burning too rich.
'76 Birchaven
Caldwell, TX
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| Re: Need Help With Suburban Furnace Adjustment [message #104912 is a reply to message #104907] |
Wed, 03 November 2010 09:52  |
idrob
Messages: 645
Registered: January 2005
Location: Central Idaho
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| pistolnut wrote on Wed, 03 November 2010 06:54 |
My '76 Birchaven by Coachmen has what appears to be the original Suburban furnace. The unit works, however it produces very noticable vapor/smoke from the exhaust port and the screen on the port has a lot of soot buildup. My manual gives the procedure for adjusting the air and therfore the flame on a different brand of furnace, can anyone tell me how to do so with the Suburban? The unit works well otherwise, I think its just burning too rich.
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There is an air shutter adjustment on the burner, but I bet you have the problem that I ran into, rust clogging the burner, which makes it run rich. No adjustment will compensate for the rust I found in mine.
http://www.gmcmhphotos.com/photos/showgallery.php?cat=4165
You have to take the entire burner out to do this repair, but I think it will work for you.
Rob Allen
former owner of '76 x-PB
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| Re: Need Help With Suburban Furnace Adjustment [message #104914 is a reply to message #104907] |
Wed, 03 November 2010 09:57 |
idrob
Messages: 645
Registered: January 2005
Location: Central Idaho
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I forgot to say, you also could have mud dauber or wasp nests in the air intake circuit which cause too little air. Again, the entire furnace must come out to check to be sure. They can be deep in the interior, in the intake fan cage.
Rob Allen
former owner of '76 x-PB
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| Re: [GMCnet] Need Help With Suburban Furnace Adjustment [message #104916 is a reply to message #104914] |
Wed, 03 November 2010 10:15 |
gmcrv1
Messages: 839
Registered: August 2007
Location: Memphis
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Rob,
For someone with pretty good mechanical abilities - approximately how long
do you think it takes to R & R the furnace and do a general cleanup as you
did? I don't think I have mud daubers in the venting ducts - I know I have
them! Your pictures are excellent!
Thanks,
Tom Eckert N2VWN
73 Glacier
Oakland, TN
On Wed, Nov 3, 2010 at 9:57 AM, Rob Allen <profmail@wildblue.net> wrote:
>
>
> I forgot to say, you also could have mud dauber or wasp nests in the air
> intake circuit which cause too little air. Again, the entire furnace must
> come out to check to be sure. They can be deep in the interior, in the
> intake fan cage.
>
>
> --
> Rob Allen
> former owner of '76 x-PB
> _______________________________________________
> GMCnet mailing list
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| Re: Need Help With Suburban Furnace Adjustment [message #104918 is a reply to message #104912] |
Wed, 03 November 2010 10:40 |
pistolnut
Messages: 19
Registered: September 2010
Location: Caldwell, TX
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[quote title=idrob wrote on Wed, 03 November 2010 09:52]| pistolnut wrote on Wed, 03 November 2010 06:54 |
There is an air shutter adjustment on the burner, but I bet you have the problem that I ran into, rust clogging the burner, which makes it run rich. No adjustment will compensate for the rust I found in mine.
http://www.gmcmhphotos.com/photos/showgallery.php?cat=4165
You have to take the entire burner out to do this repair, but I think it will work for you.
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I'll bet that is my problem. Those photos are great!  I saw where that cover is located, does the burner just slide out? Are there not burners in the adjacent sections of the heat exchanger?
'76 Birchaven
Caldwell, TX
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| Re: Need Help With Suburban Furnace Adjustment [message #104928 is a reply to message #104907] |
Wed, 03 November 2010 12:49 |
fred v
Messages: 999
Registered: April 2006
Location: pensacola, fl.
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i have a Coachman Royal with that unit. i've had mine out several times. download the manuals for the Suburban furnace here:
http://bdub.net/manuals/index.html
the installation instructions will show you what screws need to be removed to remove the unit. basically one outside at the vent and 2 that hold the case to the floor. unplug the wires harness and remove the copper gas supply tube and remove the gas valve. it is sometimes tricky going back in to get the vent pipes lined back up with the vent fitting.
the duct hoses slide into grooves in the case and are fussy to get out and back in. sometimes they have screws that hold in the grooves.
good luck,
Fred V
'77 Royale RB 455
P'cola, Fl
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| Re: [GMCnet] Need Help With Suburban Furnace Adjustment [message #104964 is a reply to message #104916] |
Wed, 03 November 2010 17:09 |
idrob
Messages: 645
Registered: January 2005
Location: Central Idaho
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| gmcrv1 wrote on Wed, 03 November 2010 08:15 |
Rob,
For someone with pretty good mechanical abilities - approximately how long
do you think it takes to R & R the furnace and do a general cleanup as you
did? I don't think I have mud daubers in the venting ducts - I know I have
them! Your pictures are excellent!
Thanks,
Tom Eckert N2VWN
73 Glacier
Oakland, TN
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Kind of depends on how buried your furnace is, the various cabinets make that the most time consuming part of the job in general. I would allow half a day for the work, at least. Especially for your first time to take it out.
BTW, the newer Suburban furnaces do not have a cast iron burner, it is now stainless steel. I don't know when the change was made though.
Also look for a red stripe on the rubber tube that connects the burner area to the combustion fan. The original tubes cracked, and made the furnace unsafe, the red stripe rubber tube was the recall replacement. No parts are now available for these older furnaces, including the recall parts. If you don't have the red stripe rubber tube, make a very very close inspection of the one you have. Better yet, replace the entire furnace. Dead is not good.
Rob Allen
former owner of '76 x-PB
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| Re: Need Help With Suburban Furnace Adjustment [message #104966 is a reply to message #104918] |
Wed, 03 November 2010 17:23 |
idrob
Messages: 645
Registered: January 2005
Location: Central Idaho
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[quote title=pistolnut wrote on Wed, 03 November 2010 08:40]| idrob wrote on Wed, 03 November 2010 09:52 |
| pistolnut wrote on Wed, 03 November 2010 06:54 |
There is an air shutter adjustment on the burner, but I bet you have the problem that I ran into, rust clogging the burner, which makes it run rich. No adjustment will compensate for the rust I found in mine.
http://www.gmcmhphotos.com/photos/showgallery.php?cat=4165
You have to take the entire burner out to do this repair, but I think it will work for you.
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I'll bet that is my problem. Those photos are great! I saw where that cover is located, does the burner just slide out? Are there not burners in the adjacent sections of the heat exchanger?
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I always work on my furnaces out of the coach, on the bench. I can't recall exactly how the burner comes out now, I think it just slides out, but I have worked on so many with slight differences I would not bet on it at this point. Suburban furnaces are not really disassembly friendly, and a lot of running changes were made over the years.
There is only one burner, the gasses from it are routed through the other sections of the heat exchanger and then exhausted out to the exterior. The combustion chamber is under positive pressure from the combustion fan so any leaks will put gasses into the coach. If you find a lot of rust in the combustion chamber be wary that it may have rusted through and will let gasses into the coach. I had one Suburban that gave me violent headaches. I fount the combustion chamber had rusted through. When in doubt, please, please replace the furnace. They can be dangerous, and any 35 year old furnace has paid it's dues.
I have said this a number of times here on the net. I had a cousin and his wife and daughter killed with a furnace Carbon Monoxide issue (not a Suburban or RV furnace). It was not a nice way for three people to die, so I always err on the side of caution.
Rob Allen
former owner of '76 x-PB
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| Re: Need Help With Suburban Furnace Adjustment [message #104970 is a reply to message #104966] |
Wed, 03 November 2010 17:58 |
fred v
Messages: 999
Registered: April 2006
Location: pensacola, fl.
Karma: 0
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[quote title=idrob wrote on Wed, 03 November 2010 17:23]| pistolnut wrote on Wed, 03 November 2010 08:40 |
| idrob wrote on Wed, 03 November 2010 09:52 |
| pistolnut wrote on Wed, 03 November 2010 06:54 |
There is an air shutter adjustment on the burner, but I bet you have the problem that I ran into, rust clogging the burner, which makes it run rich. No adjustment will compensate for the rust I found in mine.
http://www.gmcmhphotos.com/photos/showgallery.php?cat=4165
You have to take the entire burner out to do this repair, but I think it will work for you.
|
I'll bet that is my problem. Those photos are great! I saw where that cover is located, does the burner just slide out? Are there not burners in the adjacent sections of the heat exchanger?
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I always work on my furnaces out of the coach, on the bench. I can't recall exactly how the burner comes out now, I think it just slides out, but I have worked on so many with slight differences I would not bet on it at this point. Suburban furnaces are not really disassembly friendly, and a lot of running changes were made over the years.
There is only one burner, the gasses from it are routed through the other sections of the heat exchanger and then exhausted out to the exterior. The combustion chamber is under positive pressure from the combustion fan so any leaks will put gasses into the coach. If you find a lot of rust in the combustion chamber be wary that it may have rusted through and will let gasses into the coach. I had one Suburban that gave me violent headaches. I fount the combustion chamber had rusted through. When in doubt, please, please replace the furnace. They can be dangerous, and any 35 year old furnace has paid it's dues.
I have said this a number of times here on the net. I had a cousin and his wife and daughter killed with a furnace Carbon Monoxide issue (not a Suburban or RV furnace). It was not a nice way for three people to die, so I always err on the side of caution.
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yes, rust, i forgot to mention that. when you get the unit out you can turn it over and shake it to direct the rust through the plenum chambers and dump it out. if you look closely at the plenum you will see how the three chambers are connected together. rotate it to make the rust pass through the connector holes. look for rusted out spots.
Fred V
'77 Royale RB 455
P'cola, Fl
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| Re: Need Help With Suburban Furnace Adjustment [message #104978 is a reply to message #104970] |
Wed, 03 November 2010 18:55 |
stick miller
Messages: 1036
Registered: March 2010
Location: Americus, Georgia
Karma: 0
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Senior Member |
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To carry this conversation a bit further, I have a '78 Royale Coachmen conversion. The furnace is relatively accessible from a cabinet in the mid cabin, but I'm not sure it needs to come out. My manual says that the blower should run if the thermostat is raised up above the room temperature. I don't even have a blower working and I think that needs to happen before I do more. What should I look for?
Stick Miller
'78 Royale - "White Trash" - she left me for another man
'76 Eleganza - "Cousin Eddie" Sold
'84 Bluebird Wanderlodge - "Past Tents"
Americus, GA
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| Re: [GMCnet] Need Help With Suburban Furnace Adjustment [message #104999 is a reply to message #104964] |
Wed, 03 November 2010 21:10 |
gmcrv1
Messages: 839
Registered: August 2007
Location: Memphis
Karma: -1
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Senior Member |
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Rob,
I haven't taken the slightest look at the furnace. But, before I use it I
want to pull it out and inspect it. From your reply, I will take a very
close look and if any doubt I'll either replace it with a new unit or
substitute a couple of small electric/ceramic heaters.
Thanks for the reply.
Tom Eckert N2VWN
73 Glacier
Oakland, TN
On Wed, Nov 3, 2010 at 5:09 PM, Rob Allen <profmail@wildblue.net> wrote:
>
>
> gmcrv1 wrote on Wed, 03 November 2010 08:15
> > Rob,
> >
> > For someone with pretty good mechanical abilities - approximately how
> long
> > do you think it takes to R & R the furnace and do a general cleanup as
> you
> > did? I don't think I have mud daubers in the venting ducts - I know I
> have
> > them! Your pictures are excellent!
> > Thanks,
> >
> > Tom Eckert N2VWN
> > 73 Glacier
> > Oakland, TN
>
>
> Kind of depends on how buried your furnace is, the various cabinets make
> that the most time consuming part of the job in general. I would allow half
> a day for the work, at least. Especially for your first time to take it
> out.
>
> BTW, the newer Suburban furnaces do not have a cast iron burner, it is now
> stainless steel. I don't know when the change was made though.
>
> Also look for a red stripe on the rubber tube that connects the burner area
> to the combustion fan. The original tubes cracked, and made the furnace
> unsafe, the red stripe rubber tube was the recall replacement. No parts are
> now available for these older furnaces, including the recall parts. If you
> don't have the red stripe rubber tube, make a very very close inspection of
> the one you have. Better yet, replace the entire furnace. Dead is not
> good.
>
> --
> Rob Allen
> former owner of '76 x-PB
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: Need Help With Suburban Furnace Adjustment [message #105026 is a reply to message #104978] |
Thu, 04 November 2010 07:53 |
fred v
Messages: 999
Registered: April 2006
Location: pensacola, fl.
Karma: 0
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Senior Member |
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| Stick Miller wrote on Wed, 03 November 2010 18:55 |
To carry this conversation a bit further, I have a '78 Royale Coachmen conversion. The furnace is relatively accessible from a cabinet in the mid cabin, but I'm not sure it needs to come out. My manual says that the blower should run if the thermostat is raised up above the room temperature. I don't even have a blower working and I think that needs to happen before I do more. What should I look for?
|
the blower comes on, the sail switch closes and powers the circuit board which opens the gas and starts the spark. that's the sequence.
sounds like you need to check for 12v at the wire connection to the unit. if you have voltage i'd pull the unit out and do bench testing. replacement boards are available. there is also a paper in the GMCES tech. page called:
Operating and Troubleshooting the Suburban Dyna-Trail Furnace by John Nicholls.
it has some pictures of the burner being removed and other tips.
Fred V
'77 Royale RB 455
P'cola, Fl
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| Re: Need Help With Suburban Furnace Adjustment [message #105028 is a reply to message #105026] |
Thu, 04 November 2010 08:00 |
stick miller
Messages: 1036
Registered: March 2010
Location: Americus, Georgia
Karma: 0
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Senior Member |
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Thanks - I just wondered if I'm missing something like a switch similar to the switch that cuts the gas water heater on and off. I'll test the electrical first. I do know that it worked last winter. I may just be missing something.
If I understand correctly, the only on/off switch is the thermostat on the cabin wall.
Stick Miller
'78 Royale - "White Trash" - she left me for another man
'76 Eleganza - "Cousin Eddie" Sold
'84 Bluebird Wanderlodge - "Past Tents"
Americus, GA
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| Re: Need Help With Suburban Furnace Adjustment [message #105033 is a reply to message #105028] |
Thu, 04 November 2010 09:22 |
pistolnut
Messages: 19
Registered: September 2010
Location: Caldwell, TX
Karma: 0
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Junior Member |
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| Stick Miller wrote on Thu, 04 November 2010 08:00 |
Thanks - I just wondered if I'm missing something like a switch similar to the switch that cuts the gas water heater on and off. I'll test the electrical first. I do know that it worked last winter. I may just be missing something.
If I understand correctly, the only on/off switch is the thermostat on the cabin wall.
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On mine, the previous owner had added a toggle switch near the furnace so that it could be positively turned off. I think my furnace can run with out shore or generator power so if you forget to turn it off at the thermostat it can cycle and run the house battery down.
I removed and cleaned my burner and its working much better now. Flames look good. Didn't find a bunch of rust except from the burner itself. I cleaned it up with the hacksaw and a wire brush. I'm purchasing a CO monitor to be safe, however. Lowes has a CO and propane monitor for about $60.00
'76 Birchaven
Caldwell, TX
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| Re: Need Help With Suburban Furnace Adjustment [message #105036 is a reply to message #105033] |
Thu, 04 November 2010 10:39 |
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mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
Karma: 0
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Senior Member |
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| pistolnut wrote on Thu, 04 November 2010 07:22 |
| Stick Miller wrote on Thu, 04 November 2010 08:00 |
... If I understand correctly, the only on/off switch is the thermostat on the cabin wall.
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On mine, the previous owner had added a toggle switch near the furnace so that it could be positively turned off. I think my furnace can run with out shore or generator power so if you forget to turn it off at the thermostat it can cycle and run the house battery down. ...
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My '78's furnace will run the fan with the thermostat OFF. I am fairly sure that it has a bad temp sensor and "thinks" it needs to run the fan to cool off the heat exchanger... I need to pull it out and fix it... someday. But until then, it is unplugged. It WILL run the house battery dead.
Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
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| Re: Need Help With Suburban Furnace Adjustment [message #105049 is a reply to message #105028] |
Thu, 04 November 2010 12:25 |
idrob
Messages: 645
Registered: January 2005
Location: Central Idaho
Karma: 0
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Senior Member |
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| Stick Miller wrote on Thu, 04 November 2010 06:00 |
Thanks - I just wondered if I'm missing something like a switch similar to the switch that cuts the gas water heater on and off. I'll test the electrical first. I do know that it worked last winter. I may just be missing something.
If I understand correctly, the only on/off switch is the thermostat on the cabin wall.
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Check the 12 volt power to the furnace. Check the GROUND also. By pass the thermostat by twisting the wires together. If it then starts, you have some thermostat issue. There may be a delay in starting, depending on how your furnace was built. Suburban used several systems, some start immediately, some have a 10 to 30 second delay after the thermostat is activated.
If that does not get it working, let us know and we can offer more (deeper in the furnace) ideas. But since yours does not start at all, most likely the issue is external to the unit. Tell us if it is a pilot light model, or an electronic ignition one. That makes a difference in how they operate and how to diagnose them.
Rob Allen
former owner of '76 x-PB
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| Re: Need Help With Suburban Furnace Adjustment [message #105051 is a reply to message #105033] |
Thu, 04 November 2010 12:29 |
idrob
Messages: 645
Registered: January 2005
Location: Central Idaho
Karma: 0
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Senior Member |
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| pistolnut wrote on Thu, 04 November 2010 07:22 |
I removed and cleaned my burner and its working much better now. Flames look good. Didn't find a bunch of rust except from the burner itself. I cleaned it up with the hacksaw and a wire brush. I'm purchasing a CO monitor to be safe, however. Lowes has a CO and propane monitor for about $60.00
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Glad it is working better now. Cleaning made a world of difference in mine too. The CO/Propane monitors generally require house power (120 volts) to operate. They may have a battery backup, but it is a short life battery so look at what you are going to buy carefully prior to spending the money.
Rob Allen
former owner of '76 x-PB
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| Re: Need Help With Suburban Furnace Adjustment [message #105086 is a reply to message #105049] |
Thu, 04 November 2010 19:07 |
stick miller
Messages: 1036
Registered: March 2010
Location: Americus, Georgia
Karma: 0
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Senior Member |
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If that does not get it working, let us know and we can offer more (deeper in the furnace) ideas. But since yours does not start at all, most likely the issue is external to the unit. Tell us if it is a pilot light model, or an electronic ignition one. That makes a difference in how they operate and how to diagnose them.
Mine has an electronic ignition. I'm going to check fuses, etc. & probably rely on Ken Henderson for some expert help.
Stick Miller
'78 Royale - "White Trash" - she left me for another man
'76 Eleganza - "Cousin Eddie" Sold
'84 Bluebird Wanderlodge - "Past Tents"
Americus, GA
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| Re: Need Help With Suburban Furnace Adjustment [message #105715 is a reply to message #105086] |
Thu, 11 November 2010 17:05 |
stick miller
Messages: 1036
Registered: March 2010
Location: Americus, Georgia
Karma: 0
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Senior Member |
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Quick follow up on the furnace. When all else fails, read the directions. The furnace does have a delay. I followed the procedure exactly and have heat. It's a bit noisy so I'm going to try and lubricate the squirrel cage without blowing the coach up.
We don't have real cold weather here, but it'll be nice to have something to take the chill off. I've already bought a CO detector to sit beside the propane sniffer.
Thanks for the help and encouragement. Nothing really seems to be wrong with this coach. Everything is just complicated!
Stick Miller
'78 Royale - "White Trash" - she left me for another man
'76 Eleganza - "Cousin Eddie" Sold
'84 Bluebird Wanderlodge - "Past Tents"
Americus, GA
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| Re: [GMCnet] Need Help With Suburban Furnace Adjustment [message #105728 is a reply to message #105715] |
Thu, 11 November 2010 19:18 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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Stick,
Everything is NOT complicated, you're mechanically declined, just like I'm
electrically declined! ;-)
The learning curve when one buys a GMC is VERY steep AND never ending!
There's always a new challenge around the next corner!
Once you get used to it you will be addicted like the rest of us!
All the best,
Rob M.
USAussie
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org
[mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Stick Miller
Sent: Thursday, November 11, 2010 5:05 PM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Need Help With Suburban Furnace Adjustment
Quick follow up on the furnace. When all else fails, read the directions.
The furnace does have a delay. I followed the procedure exactly and have
heat. It's a bit noisy so I'm going to try and lubricate the squirrel cage
without blowing the coach up.
We don't have real cold weather here, but it'll be nice to have something to
take the chill off. I've already bought a CO detector to sit beside the
propane sniffer.
Thanks for the help and encouragement. Nothing really seems to be wrong with
this coach. Everything is just complicated!
--
Stick (I used to be skinny) Miller
'78 Royale
Americus, Georgia
http://www.gmcmhphotos.com/photos/showphoto.php?photo=35133
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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