Furnace doesn't light

[Usmcone]

Atwood furnace blower runs but does not light up. Any suggestions on trouble shooting?

[shiggs68]

Does the blower shutdown or continue to run?

If it shuts down, that indicates it did not move enough air to trip the sail switch. Low battery, restricted heat registers, or dirty or bad sail switch are the common causes.

If it continues to run, that indicates the burner did not fire or the fire was not detected. Assuming you have propane, the most common causes are debris or bug nests in the burner area or poor alignment of the igniter/sensor rod.

Here is an Atwood Service Manual http://bryantrv.com/docs2/docs/hflamefurn04.pdf


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[Usmcone]

Thanks for your reply. It continues to run. Your input tells me the direction to check.

[speed racer]

Low voltage (12v) or bad connections.

[mrwrench]

replace the module board/ ignitor

[mrwrench]

remove the board and have it tested by any rv dealer ,

[wa8yxm]

Worked this up when My furnace quite.. NOTE: In my case it was the very well named Mother board (Control board) that was bad. I opted for a Dinosaur board replacement.. Glad I did. Very well built here in the USA buy folks who take pride.. And even the design is better.

When the T-Stat calls for heat the control board starts the blower (1)
The blower blows closing the sail switch (2)
The control board then opens the gas valve (3) and begins sparking (4.1)
Gas Flows (5) And ignitets (4.2)
The flame heats the flame sensor (5)
The flame sensor sends .480 volts to the control board (6)
which then detects the .480 and continues operation (*)
When the T-stat says "Enough already" (RV is now warm)
The control board shuts off the gas flow (*)
and then turns off the blower after a cool down (*)

*: At nearly every step the control board is involved. IF IT IS BAD, things will not work.. I recommend replacement boards from Dinosaur boards.. When Mine went out the Dino board was less than half the price and when opened the box the quality of construction and workmanship, and then design was very clear to my trained eyes.

1: No 12 volt to furnace, blower motor shot
2: Low 12 volt, air ducts clogged, blower "obstructed" bad sail switch
3: Bad solenoid, Clogged Gas Jet
4: .1: Bad ignition circuit (high voltage) on control board. .2: Points too wide (Very common it seems)
5: These do not often fail but they can
5: Bad connection, NOTE:
5 and * Bad wire.

* applies to all steps by the way So does bad wire/connection.

[Northernaire]

I had the same problem. It was the relay.

You should have 12V coming from the board 12V from the T/Stat. If you have those, jumper from the 12V from the board to the one going to the burner. If it fires up it's the relay.

[TonyMac]

Mine was the sail switch. Blower start, burner doesn't light, blower quits.

[W4KMA]

X2 on sail switch. Short wires going to sail switch and see if it starts.