Atwood Furnace Wont Light

Jim,does the furnace smell like propane outside when it attempts to ignite? The one I was working on did, so that told me propane supply was not a problem, like I thought. The voltage at the batteries was 12.9, so voltage was not a problem. I pulled the burner out today, the burner assembly itself was pretty much rotten and rust had actually gotten between the electrode and ground, replaced em and done, firing on first spark like a champ.

The assembly is not hard to take out. Like you said 2 screws in the back and 1 on the bottom left, and theres 1 in the front that holds the bottom shelf in,you'll seeit. Disconnect gas line, unplug 2 wires, and pull assembly out. I hope you aren't paying service tech, since unit is only 7months old, it is good to know how it works though. Basically spark and fuel.

When ours started doing these off and on strange things, it was the circuit board. Replaced and has worked fine for 2 years now.

Hello, I am having a similar issue. My 8535 Atwood furnace is 7 months old. First it got intermittent on lighting and I honed in on a works on one tank, not the other. That turned out not to be the case. Checking pressure at the gas valve found it was 8.5"wc. Turned regulator to read 11"wc at furnace gas valve. Furnace lit. OK, worked for a couple days. Now, if I leave the furnace off overnight, it will light once in the morning and run till it satisfies the thermostat which yesterday was 40 minutes. Then when the thermostat calls for more heat it will not light and go into the 3 plink soft lockout.

After it lights the first time in the morning, goes into the 3 blink/one hour lockout it tries to light every hour. Sometimes after 3-4 attempts/hours it will light and work normally for that heat cycle. Then it will not light the rest of the day.

When it did not light we did try a replacement board and that did not correct the issue. We are thinking electrode ceramic cracked, air gap? The service tech has a electrode ordered.

While waiting on the electrode, I'd be willing to pull the burner assy out and check the gap. It looks like you take out 2x 1/4" sheet metal screws way up in there and undo the gas line, remove the electrode wire and gas valve wire.

Can the burner assy be removed using the above method?

Since it worked perfect for a couple of months, I find it hard the gap changed and the only working one time in the morning has me stumped.

Thanks Jim

From Atwood (Hydro Flame) manual:

"When an electrode assembly is installed on a furnace, they will
already be in a fixed and predetermined position above the burner.
The only adjustment that you may need to do is on the sparking and
ground electrode points. This gap should be 1/8 ?

Someone saved me the typing of my boilerplate.

Suspect in this case is spark gap on the ignition system.

Since once it lights, it runs.. There are actually two suspects.
My Number one (Seen it twice on two entierly different types of furnaces, one Atwood, one Lenox yes, the folks who make 'em for the sticks and bricks) is spark gap, the Atwood was 2x factory spec, the Lenox 4x, I'm amazed it lit at all.

Reset both and they have worked properly ever since. (Well the board failed on the Atwood, but that may be related or not... I know Dinosaur boards designed in a protection against what I think happened... Which is 1 of the reasons I recommend them when you replace boards).

To re-set you MUST have the manual so you can do it right.


Option 2 is a partial clog of the gas jet... Might as well check it while you are checking the gap, 90% of the labor is the same, (if you reverse it it is 99%) since you have to remove the burner assembly to check the gap.

Yes the high tension wire is the Red one from circuit board to spark electrode.

After the fan comes on a timing circuit is activated for purge cycle.....then power goes to spark electrode and gas valve at same time. The 'clicking' you heard is the spark (electrode tip to ground rod) and smelling ga means gas valve has opened.
IF main flame lit you would hear it.....just clicking means that main flame is not lighting off. Could be obstruction in main burner (dirt/rust), could be spark electrode dirty, could be cracked ceramic.

Here is a Atwood Manual that covers the three series (79,85,89) of furnaces.......LINK

I think the series of events occur in this sequence.

The switch is turned on which activates the fan motor

The fan blows against the sail switch which then activates the ignitor, this is where the 12 volt voltage comes to play, if the fan does not turn fast enough the sail switch will fail to activate the ignitor.

Then the gas valve activates to complete the cycle.

If the sail switch goes bad, or the circuit board, no ignition will occur.

You can call an independent or mobile rv repair person and they will sometime assist you through a proper diagnostic procedure. Also some rv repair places have a circuit board tester that can rule out whether you have a circuit board on the blink. Replacing parts without a proper diagnosis can get expensive.

Also, you are correct, I've heard of a number of cases where the cold had effected the propane flow. A few have heated the propane tanks with a blow dryer or other means, to find it resolved some issues.

Thanks for the responses. I'm not leaning towards propane, because I can smell it, actually I'm surprised by the amount of propane I smell. It has been below freezing the past few weeks, and I know propane can get strange when it's cold.

I'm thinking there is no flame, wouldn't I hear it even if it lit for a few seconds? I thought it was odd that it didn't fire with the cover on, I'm thinking that was just coincidence, cause I couldn't get it to fire with the cover off again, it had been running intermittently. The back of this unit is a real PITA to access it's in the basement behind a wall that has to be removed.

The high tension wire is the red one that runs from the circuit board to the electrode, correct?? And what exactly makes the clicking sound? Thanks

Atwood Fault Codes


Fault...............................LED Indication

Internal Circuit Board fault-------------Steady on, no flashing

Limit switch/Airflow problems-----------1 flash with 3-second pause

Flame Sense fault--------------------2 flashes with 3-second pause

Ignition Lockout Fault----------------3 flashes with 3-second pause


You are having an ignition lockout fault.
That would mean that the electronics is not detecting a flame that MAY be there.
Maybe a bad ground.
Or, the sparking you hear may not be taking place at the place it should be.
Possibly a bad spark electrode or high tension wire.

The other thing is it not firing/refiring with cover in place.
That suggests an air flow imbalance....blockage in combustion/exhaust chamber
Or possibly a cracked heat exchanger

LP Detector
RED light...Alarm along with LOUD BEEP
Green Light.....All good
Yellow Light......thought that was an indication that LP Detector should be replaced.

Low voltage is not occurring at 12.9V

2007 year rig.....detector probably is on last legs. They have a self life (sensor) and should be replaced 5-7 yrs

I ran into this recently. I found a combination of issues that were similar to those you've described. The issue I found was a faulty propane regulator. It would light and run shortly, or not light at all. Got it lit once and was checking the regulator and it would pulse from green to red and then back to green then the heater would shut down.

Purchased a new regulator and it lit right up and has worked perfect since.