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Old 01-12-2019, 12:25 PM   #1
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Join Date: Aug 2018
Location: Dunwoody, GA
Posts: 18
Furnace not heating coach well

Hi - We have a 2003 Monaco Knight 34í. We bought it used last year so we donít have any history. The coach seems to be in very good shape. Everything worked except for the furnace. Took it to Camping World and they replaced the furnace circuit board. It does look very dirty and dusty for a new board however. The furnace is a Atwood 8535-IV-DCLP. We ran the furnace for 4 hours. It only raised the temperature maybe 1 degree per hour from 55-59 degrees. It never got over 60 degrees. The outside temperature was in the low 40s. The furnace was always on and blowing cold to warm air. I could feel constant hot exhaust on the outside exhaust. No carbon on the exhaust port. The middle and back registers were warm. The front register, in back of the passenger seat, was blowing cold air for a long time. It finally blew warm air after a couple of hours. I checked the basement. Didnít detect or see any leaks. The basement has a large plastic rectangular box that runs the length of the coach, so I was not able to inspect ducting inside. We have vacuumed out all ducts and replaced the vent covers. Those were all open. Inspected the ducts from the registers and didnít see any obstacles. The ducting in the floor seems to be very shallow and small for such a large RV. We have Reflectix on all windows. Sealed around the furnace where it goes into the floor with silver duct tape. On our old cheap trailer the furnace would get everything toasty warm in 15-20 minutes. Getting ready to go to Alaska this year so we are interested in fixing the heating problem. Thinking of replacing the whole furnace with maybe a newer or bigger unit. Any thoughts or advice would be greatly appreciated.

2003 Monaco Knight 34'
2014 Honda CR-V EX-L
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Old 01-12-2019, 01:25 PM   #2
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Join Date: Oct 2016
Posts: 1,097
Hi UP2LATE; I checked the Knight brochure for 2002 and 2004 since 2003 does not show up on the Monaco web site. Your furnace is supposed to be 35K BTU. On MY Monaco 01 Windsor 34' I have a 42K BTU furnace. Mine warms up in a matter of minutes. My brother in law had a 2003 Holiday Rambler Neptune that is the cousin to the Knight. His was 34' also. Was the same furnace as yours and his heated fine as I remember. When my furnace is running the air coming out of the exhaust is warm, not hot as you described. I am sure we can agree that we will have differences in opinion of what is warm and what is hot. To me, I think that you have some kind of blockage somewhere in the system that is not allowing the air to move from the furnace plenum down stream through the vents and is blowing some air back through the furnace exhaust. I don't know if that is even possible. You might have to dismantle the furnace itself to get a good look at everything. I you have an infrared digital thermometer, you might want to check temperatures down stream from the furnace and see if you can find a big loss of the heat somewhere. This is the only thing that comes to mind. Hope others here with your coach will respond.

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Old 01-12-2019, 11:18 PM   #3
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Atwood 8535-IV-DCLP is a 35,000 btu furnace (actual btu is 34K)

Motor drives 2 separate wheels
*1 for combustion air....blows thru heat excahnger
*1 for room air......blows around heat exchanger then into discharge plenum/duckwork
The 2 are not connected....and if they do it is because heat exchanger has cracked and CO would be blown into inside of RV!!!

IF the ducts were obstructed/blocked then heat exchanger would get too hot and the High Temp Limit Switch would open shutting down furnace until exchanger cooled down...then it would close and furnace would refire....repeat
SO doubt ductwork is issue

Sounds more like LACK OF HEAT....flame too cold/low propane system pressure OR dirty/obstructed orifice/burner

I suspect it is Low Propane System Pressure.....furnace is a big propane hog.
Higher btu then water heater/fridge and stove top burners combined

Got to have the correct system pressure in order for furnace to burn hot enough to cause good heat exchange.
Main LP Reg should HOLD 11" WC with at least 50% of propane appliances in service.

1st thing .....get LP system pressured tested
2nd thing.....clean up burner/orifice (do NOT poke thru orifice or use High Pressure Air to blow thru it......metered hole that is critical for proper fuel/air mixture)
Is it time for YOUR Medication or Mine?
Dodge 3500 w/Tractor Motor & NUWA 5vr
US NAVY---USS Decatur DDG-31
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Old 01-16-2019, 01:04 AM   #4
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On my old coach, the main duct coming from the furnace was crushed underneath the kitchen cabinet. They tried to fit the duct underneath the 2X4 used for the cabinet platform base. It crushed the 4-inch duct down to about 2 inches max. I had to remove the cabinet floor and I redid it myself.
J.C. "Tinstar 1114"
2002 Monaco Windsor M-36PBD
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Old 01-16-2019, 08:46 AM   #5
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Location: McCleary,wa
Posts: 363
I have 2 atwood furnaces 25btu I think, one cycles, the burner comes on ,gets hot(never really up to temp) then burner shuts off until it cools down, then starts burner again and runs for awhile, cycle,cycle etc, the other works fine, comes up to heat setting and turns off. I have replaced the limit switch, control board with same result. It does give an alarm of intake air restriction if I am looking at the furnace from outside when it cycles, pulled entire top off furnace and same result. It cycles and never does get really hot. Others have said there's cycle too. It's just for rear of coach and don't use it much so haven't found solution, if it was my only furnace I would have to fix it. Maybe later,,, I'm retired!
John and Cherrie
2003 Holiday Rambler Scepter 40DST
Pushed By 2003 Ford Explorer
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Old 01-16-2019, 09:10 AM   #6
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Sounds like your burner is cycling on and off while the blower motor keep's running.

Neal and Deb + Mya and Gizmo, the pup's
2003 Winnebago Sightseer 30B

May the roads rise up to meet you, May the winds be always at your back...
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furnace, heating, heat, ace

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