Atwood AFMD35131 furnace

[Bookem15]

I have an Atwood AFMD35131 furnace and I have replaced the circuit board and the igniter but still not flame. The blower comes on, I hear the gas valve click and smell gas but it does not try to light. It goes into ignition lockout (light blinks 3 times). The sail switch is clean and free of debris and the high temp switch test fine. Anyone have any ideas on what to try next?

 

[jsb5717]

Could be a couple things.

First, if it's attempting to light or the gas valve opens then you already know that the sail switch and Limit switch are both OK.

When you say you replaced the igniter are you talking about the electrode attached to the propane valve? The igniter is attached to the circuit board.

Do you hear any clicking at all from the ignition like it wants to light but won't ignite into flame? If the gas valve is opening but the igniter isn't sparking then I would still suspect the main circuit board since both the igniter and gas valve are called into service at the same time once the sail switch closes. You might give a good inspection to all of the wiring to make sure they are all replaced and fully seated.

Beyond that I'm stumped. The opening gas valve but no ignitor points to the main board or wiring. If you pulled out the propane valve to replace the electrode did you re-attach the black ground wire? Just spit-balling

 

[Bookem15]

I changed the igniter that has one wire that attaches to the circuit board with one wire. I have tried 2 circuit boards with same results. No clicking like it is trying to light. I ordered a new sail switch just in case but I am stumped as well.

 

[Viper02]

Did you set the gap on that Ignitor when you replaced it? Since you have replaced the control board its logical to assume the issue is elsewhere... What did the burner section look like when you replaced the ignitor...

 

[Bookem15]

I have proper gap on igniter but I did not pull burner. If igniter was at least clicking I would have pulled it to check it but it's not even clicking to attempt to fire off. I ordered new sail switch just in case.

 

[Kyle and Lisa]

Remove and check the exhaust pipe for debris, such as dirt dabber nest, no flow, no go.

 

[Daryles]

I have proper gap on igniter but I did not pull burner. If igniter was at least clicking I would have pulled it to check it but it's not even clicking to attempt to fire off. I ordered new sail switch just in case.

Make sure the burner is clean at the tip of the igniter for a good Conductor surface and 1/8" gap for the spark. If the igniter is touching the surface (or corrosion) no spark, you will not hear it snap, snap, snap as it attempts to ignite.
Make sure the ground (surface return current) is clean under the mounting screw of the igniter and burner.
Remove every wire you can touch and clean the contacts with fine sand paper or an emmory (finger nail) board.

Sail switch is probably good. It has to pass that test before the gas valve will open.

There is a furnace manual in the files section.

Dinosaur Make excellent control boards.

Here is a troubleshooting chart.

 

[Bookem15]

Remove and check the exhaust pipe for debris, such as dirt dabber nest, no flow, no go.

Exhaust is clear as well

 

[Lhinkle114]

We had a similar problem with our dometic, now Atwood. Did the same things replaced board, limit switch, and sail switch then saw the video below. Then replaced burner and igniter and it worked.

https://youtu.be/AB69oqtSiwc

 

[Bookem15]

We had a similar problem with our dometic, now Atwood. Did the same things replaced board, limit switch, and sail switch then saw the video below. Then replaced burner and igniter and it worked.

https://youtu.be/AB69oqtSiwc

I am not getting the ticking noise from my igniter and I just put new one in. I changed igniter without removing burner so would the burner being bad like in video keep it from sparking?

 

[Lhinkle114]

It’s possible mine looked ok but was all rusted so I replaced it while I was there. The only think different from mine furnace and his was my igniter has two problems one is a ground and one is the igniter. Only the igniter is 1/8 from the burner and the ground has a larger gap

 

[Daryles]

I am not getting the ticking noise from my igniter and I just put new one in. I changed igniter without removing burner so would the burner being bad like in video keep it from sparking?

To verify the igniter is NOT touching the burner when installed, you need to remove the burner.
If it touching OR too far, it will not spark (snapping noise when the igniter activates).

 

[Bookem15]

To verify the igniter is NOT touching the burner when installed, you need to remove the burner.
If it touching OR too far, it will not spark (snapping noise when the igniter activates).

Oh ok thanks I will remove the whole assembly.

 

[Daryles]

Make sure you have propane gas rated teflon tape (yellow) and pipe dope before disconnecting gas lines.
Check for leaks when you are done.

 

[Bookem15]

Make sure you have propane gas rated teflon tape (yellow) and pipe dope before disconnecting gas lines.
Check for leaks when you are done.

Will do thanks

 

[Viper02]

Worth a watch

https://youtu.be/0t8vRuGdZLw?si=dDXlW3UpQv2eUZdx

 

[Bookem15]

I have tried nearly everything. Tomorrow I will pull the burner but I adjusted the igniter 20 times with no change. The burner being bad would not keep it from sparking so not sure what to try next.

 

[Bookem15]

Alright so the burner looks great, new ignitor, new circuit board twice, and new sail switch still no ignition. Propane valve opens as I can smell gas but still nothing.

 

[jsb5717]

Did you ever say how old of a rig you have? Given what you've said so far I'm thinking a wire or connectivity issue.

Can you take a pic or two of your furnace wiring and post it here?

 

[Bookem15]

Did you ever say how old of a rig you have? Given what you've said so far I'm thinking a wire or connectivity issue.

Can you take a pic or two of your furnace wiring and post it here?

It's a 2016 3611. I believe they sent me the wrong board. I notice the plug does not fit perfect like the old board so I am having them send another board.