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Topic: Front furnace in our 1995 U300 won’t light (Read 634 times) previous topic - next topic

Front furnace in our 1995 U300 won’t light

We have the Atwood Hydroflame 8535 III in our 1995 U300.
Turned it on the other day, the blower comes on but it never lights.
The back furnace works fine.
Has anyone had the same problem?
What are some things we should check?

Thanks,  Susan
Susan and Bob
1995 U320CSE
40'
Cummins M11
Coach build #4730
Previous Foretravel's 1996 U280, 1995 U300

Motorcade # 17974

Re: Front furnace in our 1995 U300 won’t light

Reply #1 –
Have you opened the outside door and cover? Check for obstructions in the exhaust and blower area? Loose connections? Also the sail switch could be sticking.
Bruce, Linda, and Macy
Zoey RIP 1/20/19
1999 U295 40' build #5400
2017 silver Jeep Wrangler, 1260 watts of solar on top
Moving around the country

Re: Front furnace in our 1995 U300 won’t light

Reply #2 –
Quote from: Rocky1down –
What are some things we should check?
The trouble shooting guide in the service manual contains a list of things to check.

https://rvpartsexpress.com/wp-content/uploads/2019/01/Atwood-Hydroflame-service-and-parts-guide.pdf
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Front furnace in our 1995 U300 won’t light

Reply #3 –
Quote from: Rocky1down –
We have the Atwood Hydroflame 8535 III in our 1995 U300.
Turned it on the other day, the blower comes on but it never lights.
The back furnace works fine.
Has anyone had the same problem?
What are some things we should check?

Thanks,  Susan

Inside that round black plastic cover* is a switch known as the sail switch.  It rises on the air flow closing a micro switch.  It's job is to make sure there is enough air flowing through the heat exchanger to prevent it from over heating, that and enough combustion air.  While you're in there make sure the fan turns freely.

You'll appreciate having a magnetic sheet metal screw driver.  Check the size with a socket before heading to Lowes or Home Depot. ICRS.
1992 Foretravel Grand Villa
U225 SBID Build No. 4134
1986 Rockwood Driftwood
1968 S.I.A.T.A. Spring
1962 Studebaker Lark
1986 Honda VF700C
1983 Honda VF750C
Charlie, the Dog was broken out of jail 24 Oct 2023
N1RPN
AA1OH (H)e who must be obeyed.

Re: Front furnace in our 1995 U300 won’t light

Reply #4 –
First, how far into the "run" cycle do you get--

Fan on?

Ignitor clicking? If so, for how long?

Smell propane in the exhaust?

As already posted, if the SAIL SWITCH is not closed (due to insufficient air flow) nothing other than fan will happen.

Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Front furnace in our 1995 U300 won’t light

Reply #5 –
Have you had the basement door open that is right below the furnace?  Whether you have or not make sure your coach has the door switch that controls the furnace. If equipped check this to see if it is working properly.

Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: Front furnace in our 1995 U300 won’t light

Reply #6 –
Bob is having a friend that has a heating and cooling business come look at it tomorrow.
He's pretty sure it is a problem with the sail switch because it doesn't even try to lite.
The blower runs great, just blows out cold air.
I'll post again tomorrow after his friend comes over and let everyone know what he determines.
Thanks

Susan
Susan and Bob
1995 U320CSE
40'
Cummins M11
Coach build #4730
Previous Foretravel's 1996 U280, 1995 U300

Motorcade # 17974

Re: Front furnace in our 1995 U300 won’t light

Reply #7 –
Also check all wiring connections. I had the same problem and found a loose connection. As soon as I tightened it up the furnace came on.

Re: Front furnace in our 1995 U300 won’t light

Reply #8 –
Quote from: Rocky1down –
Bob is having a friend that has a heating and cooling business come look at it tomorrow.
He's pretty sure it is a problem with the sail switch because it doesn't even try to lite.
The blower runs great, just blows out cold air.
I'll post again tomorrow after his friend comes over and let everyone know what he determines.
Thanks

Susan

Susan, if it's appropriate let Bob know that there is an aftermarket upgrade for the control board by Dinosaur electronics.  The original control board will run your batteries flat if the furnace doesn't light and you're not home.  The Dinosaur board will try three times before turning off the blower, waiting one hour and trying again before locking down.

Having dry camped in New England, and having mis-managed my battery state of charge, I can tell you that having the furnace re-start at 3:00 AM one more time allows for a full nights sleep.

My love for my cedar wardrobe in the hall?  Second is the generator start switch in the bedroom.

Art
1992 Foretravel Grand Villa
U225 SBID Build No. 4134
1986 Rockwood Driftwood
1968 S.I.A.T.A. Spring
1962 Studebaker Lark
1986 Honda VF700C
1983 Honda VF750C
Charlie, the Dog was broken out of jail 24 Oct 2023
N1RPN
AA1OH (H)e who must be obeyed.

Re: Front furnace in our 1995 U300 won’t light

Reply #9 –
Hmmm. Remote possibility but worth a try. Swap thermostats with the bedroom one.
Last month our bedroom thermostat would turn on, the furnace would go thru the purge cycle, then the  igniter lit the propane and I could hear the flame go on and after precisely 10 seconds flame went out and purge/cool down cycle. Then shutoff. Repeat after a bit.
I ended up buying a universal thermostat from our RV dealer for about $26+ tax. Now the furnace works perfect.
Nitehawk,  Demolition Lady, & our NEW master, Zippy the speeding BB cat.
1989 Grand Villa 36' ORED
Oshkosh chassis, 8.2 DD V8
2006 Saturn Vue AWD

Re: Front furnace in our 1995 U300 won’t light

Reply #10 –
To eliminate the control board swap it with the other furnace.
Unplug and reconnect all connections to wipe the contacts. Probably would do that first.
John Duld
1995 U320C SE 40'

Re: Front furnace in our 1995 U300 won’t light

Reply #11 –
Furnace guy didn't come. Can anyone tell me where the sail switch is located. Do we have to take the whole furnace out to check it. Can't find a diagram online.
Thanks.  Susan
Susan and Bob
1995 U320CSE
40'
Cummins M11
Coach build #4730
Previous Foretravel's 1996 U280, 1995 U300

Motorcade # 17974

Re: Front furnace in our 1995 U300 won’t light

Reply #12 –
Open the white metal cover.  Drop down the flat black plastic panel (has the wiring diagram glued to it).  You'll see a rounded black plastic cover.  The sail switch is mounted to the underside of rounded cover.

Photo below of my furnace with all the guts removed.  See the sail switch on the black rounded cover (upper left in photo)?

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Front furnace in our 1995 U300 won’t light

Reply #13 –
Video showing diagnosis of "no light" due to dirty sail switch (different model furnace but same principle as yours):

https://www.youtube.com/watch?v=-g3_Y7MqChE
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Front furnace in our 1995 U300 won’t light

Reply #14 –
Thanks so much, took off rounded cover, cleaned sail switch and it fired right up

Susan
Susan and Bob
1995 U320CSE
40'
Cummins M11
Coach build #4730
Previous Foretravel's 1996 U280, 1995 U300

Motorcade # 17974

Re: Front furnace in our 1995 U300 won’t light

Reply #15 –
Quote from: Rocky1down –
Thanks so much, took off rounded cover, cleaned sail switch and it fired right up

Susan
Congratulations.  Believe it or not you can remove the fan motor and replace it through that opening.  Should it ever become necessary.
1992 Foretravel Grand Villa
U225 SBID Build No. 4134
1986 Rockwood Driftwood
1968 S.I.A.T.A. Spring
1962 Studebaker Lark
1986 Honda VF700C
1983 Honda VF750C
Charlie, the Dog was broken out of jail 24 Oct 2023
N1RPN
AA1OH (H)e who must be obeyed.
 

Re: Front furnace in our 1995 U300 won’t light

Reply #16 –
Quote from: Rocky1down –
Thanks so much, took off rounded cover, cleaned sail switch and it fired right up

Susan

Good job Chuck........... photos always help,
Susan should sleep warm tonight!
Justin & Cathy Byrd
1995 U280 "Old Faithful"
36' Build #4673
C8.3 Cummins
Allison MD3060R 6 speed - retarder
Powertech 10KW  4cyl Kubota