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Topic: Furnace not igniting (Read 677 times) previous topic - next topic

Furnace not igniting

I tried running the furnace multiple times without ignition. Where should I begin my troubleshooting? Propane is on. The fan runs, sounds like something's trying to ignite. I looked behind the outside panel but there's not much exposed to see if I'm actually getting a spark.
Build 5477
99 3602 WTFE U270C

Re: Furnace not igniting

Reply #1 –
Does the stove light?  Normal flame height?
"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4

Re: Furnace not igniting

Reply #2 –
I assume it's a Atwood propane furnace. If so turn it on and go outside next to the furnace and listen to see if it's sparking. If not I would suspect the fan switch.

see ya
ken
The selected media item is not currently available.ken & dori hathaway & Big Agnes
🍺1992 U300 GrandVilla WTBI #4150 FOT FBP 2011
✨6V-92TA DDEC Parlor Coach 350HP Series 92
🏁2011 Nissan XTerra Pro-4X

Re: Furnace not igniting

Reply #3 –
Stove lights with normal height. Is there anyway to visualize the igniter?fan seems to run. Something sounding like a secondary fan switches on after about 10 seconds. Runs another few cycles before shutting down.
Build 5477
99 3602 WTFE U270C

Re: Furnace not igniting

Reply #4 –
Yes, critical diagnostic point:

Easiest to determine from outside standing next to the furnace/someone else turning it on:

Fan starts.

Then, do you hear any clicking of the igniter? The solid "click" of the propane valve opening?  Smell propane?

Basically, we need to know how far in to the run cycle it gets before failing.
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: Furnace not igniting

Reply #5 –
Ok.. so I need to replace the motor.. anybody have a sourse?
The selected media item is not currently available.
My advice and experiences are Free, you decide if they are worth anything .

John - driving Old Faithful
1994 U280 GV
C8.3, Banks, Pacbrake, 900 watts, Resonator, XLHD tow dolly
Retired Army Warrant Officer

Life is what you make of it - if it is lemons, make lemonade!
Former Coaches:
1988 GV 40' ORED 300HP CAT - 9 years
1990 Winnebago LeSharo - 3 years
2000 Newmar London Aire - 3 years (#18 of 23 produced)

Re: Furnace not igniting

Reply #6 –
Quote from: fouroureye –
Ok.. so I need to replace the motor.

John,

What diagnostic lead you to that conclusion?
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: Furnace not igniting

Reply #7 –
There was a sparking sequence without the metallic sound . I don't smell propane. It goes through 3
20 second cycles before quitting.
Build 5477
99 3602 WTFE U270C

Re: Furnace not igniting

Reply #8 –
You need to check for 12 volts to the gas valve while it is sparking, if you have 12 volts, will need to disassemble the orfice assembly and remove the orfice, it screws in and see if it may be plugged with nats, have seen that many times
previous 1984 35 ft ORED 250 HP 3208 Cat       
previous 1998 40 ft U295 CAI 325 hp Cummins
previous 2003 40 Ft u320 build #6140 450 Cummins M11.                                                         
1999 Mazda Miata
Ron, Nancy, Tipper the cat, Max The dog
1997 U 270 36 ft build number 5174 8.3 Cummins

Re: Furnace not igniting

Reply #9 –
You must have air flow, not just the fan running, there should be a limit switch on the air flow damper, without enough air flow..... gas valve wont turn on. We discovered this the hard way one night when temps hit the upper 20's.
Justin & Cathy Byrd
1995 U280 "Old Faithful"
36' Build #4673
C8.3 Cummins
Allison MD3060R 6 speed - retarder
Powertech 10KW  4cyl Kubota

Re: Furnace not igniting

Reply #10 –
Quote from: FourTravelers –
You must have air flow, not just the fan running, there should be a limit switch on the air flow damper, without enough air flow..... gas valve wont turn on. We discovered this the hard way one night when temps hit the upper 20's.

You are correct, the SAIL SWITCH must close for the PC board to open the propane valve.  But, since the igniter functions the same way, the sail switch IS closing.

So checking for power to the gas valve will tell if the valve is bad or if there is problem in the PC board or wiring from it to the gas valve.
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: Furnace not igniting

Reply #11 –
I would start by disconnecting and reconnecting the control board to be sure all those contacts are good.
JD
John Duld
1995 U320C SE 40'

Re: Furnace not igniting

Reply #12 –
Google to the rescue - first hit:

(This document incorporates all the above mentioned excellent suggestions, in a logical sequence, with photos)

http://www.rvforum.net/miscfiles/Furnace_Trouble-2.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: Furnace not igniting

Reply #13 –
Quote from: wolfe10 –
John,

What diagnostic lead you to that conclusion?

For a motor squeal, I would start by oiling the motor bushings.  Yes, it is not easy to do, but some light machine oil on a long blade screwdriver or similar on each end of the shaft will allow the oil to wick into the bushing area. 

If it doesn't work, then yes, you will need to replace the motor.

Also, verify that the fans are not hitting the housing and that there is no mud dubber nest upsetting fan balance.
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: Furnace not igniting

Reply #14 –
Beamalarm.com (RV Technical Help) offers some excellent advice:

Troubleshooting RV Furnace Problems
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: Furnace not igniting

Reply #15 –
Check, check.. oiled last winter.. then it's march.. squeel.. breaker.

Since its apart.. want to replace motor.. is there a direct replacement or.. automotive supply..

Barry's site good.. great but I couldn't find motor replacement Chuck.. remember I'm seeing impaired.so I miss a lot..
The selected media item is not currently available.
My advice and experiences are Free, you decide if they are worth anything .

John - driving Old Faithful
1994 U280 GV
C8.3, Banks, Pacbrake, 900 watts, Resonator, XLHD tow dolly
Retired Army Warrant Officer

Life is what you make of it - if it is lemons, make lemonade!
Former Coaches:
1988 GV 40' ORED 300HP CAT - 9 years
1990 Winnebago LeSharo - 3 years
2000 Newmar London Aire - 3 years (#18 of 23 produced)

Re: Furnace not igniting

Reply #16 –
Well, after all the advice you have gotten I am almost afraid to say this. My bedroom furnace is hard to light after it has been sitting without operation for a long time. I seldom use my furnaces (if it's cold outside, I am south bound). But........if I cycle the on/off switch up to 50 times (sometimes less). it finally ignites and stays lit. Then after it runs a few cycles it's good again.

You have to listen to the clicks of the igniter. It will click once to ignite and if it doesn't fire there will be a couple of other clicks in succession immediatly. After the secondary clicks I turn off the switch and back on again and keep doing this until I hear the roar of the flame.

Don't know why but never had to replace anything.
1994 U280, Build 4490
Deming, NM.

Re: Furnace not igniting

Reply #17 –
We bought a motor for our furnace from an RV dealer in Billings, MT. Temperatures were 10F and one of our two furnaces failed with the dreaded squeal and eventual failure to turn fast enough to operate properly. The motors are very specific to the particular furnace you have. If you open the plastic cover, you should be able to read the label on the fan. The dealer recommended replacement of the sail switch while the unit was apart.

A few years ago, we had a furnace that would go through the entire startup sequence, but would not light. I concluded that the sequence was complete because I could hear the spark and smell a bit of propane, but there was no ignition. The problem was damage to the flame grid caused by dauber deposits and overheating of the grid. FOT fixed the furnace and I added dauber screens to the intake/exhaust ports.
J D Stevens
1997 U295 CAI 36' Build #5085
2002 Subaru Outback
Motorcade 16869
Bellville, TX
 

Re: Furnace not igniting

Reply #18 –
Quote from: fouroureye –
...I couldn't find motor replacement...
Ask, and you shall receive.

1.  Go to this link, read through it (lots of good info), find your furnace model number.  Go to the parts section at the end, look up motor number:

http://bryantrv.com/docs2/docs/hflamefurn04.pdf

2.  Google the motor number for possible replacements.  If you have the popular 85-IV 16 or 20 furnace, this motor will probably work:

Amazon.com: Atwood 37696 Hydro Flame Replacement Motor: Automotive
As an Amazon Associate Foretravel Owners' Forum earns from qualifying purchases.
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"