Help! New Atwood 8535 Furnace won't light!

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kbfeip

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Dec 24, 2006
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148
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Discovery Bay, CA
Today I installed a brand new furnace.  It tries to light repeatedly, but can't seem to get there.  Fan spins, igniter works, fires up for a few seconds, and then you can hear what sounds like a solenoid valve shutting of.  (Gas valve?) 

If I let it, most of the time it will run like this continuously without shutting down, trying to light every few minutes or so.  A few times it did shut down an the diagnostic code read: Ignition fault code."  The last time it shut down and read:  "Internal control Failure."

I had the gas shut off prior to the install.  I've run the water heater, the stovetop burner, and the refer.  (Although the refer did take quite a while to light)  The stovetop burner flame does flash orange randomly around the perimeter of the burner occasionally...air in the lines?

Suggestions please?  If this sounds like air in the supply line to the furnace, suggestions on how to clear it?

Should I pour gasoline into the burner area to prime the furnace?  (KIDDING!)    :D

HELP!

 

Gary RV_Wizard

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At our Silver Springs FL home
The flame sensor is not sensing ignition, so the controller shuts down the gas supply. That's a safety feature. Either the flame sensor is not adjusted properly, the signal isn't reaching the control board, or the controller is defective. Since it is  anew furnace, I'd bet on the sensor being improperly adjusted. There should be instructions with the furnace for that.
 

rsalhus

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Jul 20, 2006
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1,335
I had a similar problem not long ago with a Suburban furnace in my Class A.  I was hooked up to campground shore power but had enabled the coach and chassis disconnect switches to keep both sets of batteries from getting overcharged.  (All the coach 12V and 110V appliances and outlets still work when the disconnects are enabled but nothing connected to the chassis batteries works when the chassis disconnect switch is enabled.)  The furnace fan would come on when I turned the furnace on, but it wouldn't light.  Tried it several times but it wouldn't light.  As soon as I disabled the disconnect switches, the furnace would work.  Don't know why, but it's been working well ever since.  Could it be that the furnace fan is hooked up to the coach batteries and the furnace igniter is hooked to the chassis batteries?
 

thelightners

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Jan 6, 2007
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5
Sounds like the same symptoms I was having.  Replaced the regulator and cleared the lines.  Everything works fine now.  See the thread furnace cycles continuously.
 

kbfeip

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Dec 24, 2006
Posts
148
Location
Discovery Bay, CA
Umm....I'm a bit embarrassed.

I emailed the vendor, described the problem, and he asked if I was operating the unit with the flue installed.

Nope.

I discarded this part along with all everything else on the old unit.  The new unit did not have a flue.  (If I understand correctly, the flue is the extension on the exhaust pipe, with a cross bar style cover extending out to the door on the outside of the coach)

Would this cause the problem?  Where can I get a flue?  (Hold the jokes folks, I realize I'm a prime target here)  :D

 

Gary RV_Wizard

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The flue is the part that goes out through the exterior door, right?  It serves as both air intake and exhaust pipe (the furnace draws its combustion air from outside the coach). Maybe without the flue attached, the exhaust gets sucked right back in the intake?  Or perhaps turbulence disrupts air flow?  I'm just guessing here...
 

kbfeip

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Dec 24, 2006
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148
Location
Discovery Bay, CA
I learned something new!  Here's a reply from the vendor of the Atwood Furnace:

KURT, This is your problem. The flue creates optimum back pressure for the furnace to run more efficient. Your flame is actually blowing out prematurely from too much airflow.  This flue slides in the furnace. And yes you could have used the old one. This one will correct your problem and make it safe to operate.

So I purchase a flue and all is well.  I'll post results when I get it installed.

Signed:
   
      ....the rookie....

 

kbfeip

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Dec 24, 2006
Posts
148
Location
Discovery Bay, CA
Flue installed...piece of cake!

Started on the first attempt.  Cycled it,  ran it, tested it....love it!

Runs great.  Problem solved.

Thanks for all the help.

Kurt

 

KodiakRV

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Aug 19, 2006
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1,820
Location
Florida
I wrote a month or two ago about odor problems when the furnace was running.  Nothing overpowering, but a definite irritation to nose & eyes.  I took the outside panel off, including the intake/exhaust flue to check for the possibility of mud dauber nests.  Didn't find any, but did notice that the furnace seemed to be sitting crooked and that a lateral support to the outside frame of the MH was missing/broken.  I straightened the furnace and attached a brace made from a piece of wood. 

I haven't noticed the odor problem a bit since then.  I think it must have been the alignment of the intake/exhaust pipes coming out of the furnace and their extension to the exterior.  They just slip together.
 

Gary RV_Wizard

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Your furnace gets its combustion air from the outside and sends its exhaust product there as well. There are seals in the exhaust/intake system to assure this is so - anything else is dangerous to you, the occupants of the RV.  Any smell of exhaust fumes is a sign of serious and dangerous problems!!!  It sounds as though you may have fixed the problem. but check it out carefully!
 

172ndLIB

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Dec 11, 2006
Posts
39
On the Atwood /Hydroflame 8500 series furnaces the flue is the exhuast pipe that runs under the gas valve to the outside.  The furnace requires a certain amount of back pressure from the pipe in order for the flame to stay lit.  Your parts store can order you a new one but it should have come with the furnace.  Have you thrown the box out yet???????
 
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