32 Leprechaun furnace not igniting

[32Leperchaun]

I have an Atwood Furnace AFMD30141_A, and while camping last week, it displayed common symptoms: working fine upon arrival, devolving to blower coming on, furnace igniting, blowing hot air for a few minutes then shutting down, to only blower working. The control board red light is blinking once every 3 seconds, indicating Air Flow / Limit Fault. All the ducts are clear of any blockage and there is no register to check for blockage. I turned of the propane, pulled out the burner / electrode ignitor and reset the switch. The blower blew just fine, but no clicks, no spark, no ignition. I assume the limit fault could be traced to the limit switch failing? I was not able to remove it, because I don't have a square head screw driver. A friend came by and said there was no continuity on the sail switch, so I replaced it. That did not solve the problem. It did not address what the blinking red light displayed either. A youtube video addressed the same symptoms, but was experiencing 3 blinks per 3 seconds, which indicates ignition lockout fault. He fixed the problem by replacing the control board. Based on the blinking red light error code I am seeing, wouldn't it make sense that the limit switch would have to be the source of the problem? Or...is it possible that the blinking red light codes are not always accurate?

Any ideas?

I have attached a shot of what I believe is the limit switch.

[TruckinRound]

You can easily check the limit switch with a VOM (volt ohm meter). Check across the terminals for continuity. If it measures open circuit or high resistance replace it.

[32Leperchaun]

Originally Posted by TruckinRound

You can check the limit switch with a VOM (volt ohm meter). Disconnect the wire on one side and check across the terminals for continuity. If it’s open replace it.

Ahhh...thanks, I'll give it a try.

[TruckinRound]

If the limit switch checks out ok try removing and cleaning the spark ignitor and flame sensor rods with steel wool, fine sandpaper, Emory cloth, or even a nail file board.

Also inspect the outside vent passages for dead bugs or insect nests.


https://www.irv2.com/forums/f54/furn...xt-524535.html

[32Leperchaun]

Originally Posted by TruckinRound

If the limit switch checks out ok try removing and cleaning the spark ignitor and flame sensor rods with steel wool, fine sandpaper, Emory cloth, or even a nail file board.

Also inspect the outside vent passages for dead bugs or insect nests.


https://www.irv2.com/forums/f54/furn...xt-524535.html

Thanks for the reply. Already sanded the electrodes with 400 grit wet dry until they were shiny again and made sure the gap was 1/8". Neither fixed the problem. All ducts were clear of any blockages.

[chrlydonsrf]

If the sail sw. isn't closing or the board isn't processing the closed signal the brain thinks there is an airflow issue. I carry spares for the 4 most likely failure points. Board, Sail Switch, Limit Switch and Ignitor/flame sensor. More than likely you.have a circuit board failure. I always start by checking the sail switch for continuity. If the sail switch is sending a closed signal to the board, then I assume it's a board failure. If you replace the board and it doesn't fix the problem you have a good spare board. In any case when you order a new board you should immediately replace the old board. Better to find you bought a bad board before you need it.

[32Leperchaun]

Originally Posted by chrlydonsrf

If the sail sw. isn't closing or the board isn't processing the closed signal the brain thinks there is an airflow issue. I carry spares for the 4 most likely failure points. Board, Sail Switch, Limit Switch and Ignitor/flame sensor. More than likely you.have a circuit board failure. I always start by checking the sail switch for continuity. If the sail switch is sending a closed signal to the board, then I assume it's a board failure. If you replace the board and it doesn't fix the problem you have a good spare board. In any case when you order a new board you should immediately replace the old board. Better to find you bought a bad board before you need it.

Thanks for the reply. I will be buying a multi tester today and testing continuity of the limit switch. If that is good, that would leave the electrode or the board, which ain't cheap these days! Gotta do what ya gotta do...

[32Leperchaun]

So I bought a multi-tester and tested continuity of the limit switch and the new sail switch. Both had continuity. But here's a new twist. There still was no spark to the ignitor, so I pulled out the new sail switch and manually engaged it while pressing the reset rocker switch. The ignitor sparked and I smelled propane. Hell, you could feel the heat generated from the initial ignition! But...it would not stay lit. I let it cycle many times, then turned off the reset switch, rinsed and repeated to no avail. I concluded that neither of the new sail switches is "sailing" with the "blow" generated from the fan wheel. They both have straight blades, opposed to the bent blade that was once in there, so I bent one of the new ones. It made no difference.

WTH?