Atwood 8535 Furnace

[Red-Rover]

Having trouble with my Atwood furnace. The furnace actually lights, burns for a few seconds then shuts down. Repeats three times then shuts down for good. Then display of flashing LED light on circuit board, 3 flashes then a pause. This indicates that even though I have ignition, the ignition is not sensed.
Question --- How is the ignition sensed? Is it an optical sensor? Is it a thermocouple? Is it a bimetal strip?
Could the problem be the circuit board?

[enblethen]

If the fire box gets too hot, the limit switch will open shutting down the burner.

[groundhogy]

what does the limit switch do?

[enblethen]

Dinosaur uses what seems to be better components, their workmanship is better and of course in most cases less dollars.

[Red-Rover]

Thank you all for the advice. I had this problem last year and after unplugging and reinstalling the six wire plug it operated correctly for a year. This time around, no such luck. I pulled the circuit board this afternoon and found some corrosion at a couple of soldered terminals on the back of the board. Guess I will order a board.
Most everyone seems to endorse Dinosaur brand over original, because?

[Chris_Bryant]

It can also be a burner issue.
First, I would just disconnect and reconnect the edge connector on the board, then pull the burner to check it and the igniter electrode.

[enblethen]

Check you ignitor/flame sensor for proper adjustment.
Check the ignitor/flame sensor cable for any burn marks through insulation.
Circuit board issue. As noted in earlier post, use Dinosaur Electronics replacement.

[rv_bear]

I just had a similar problem and it was the limit switch I had changed prior to this and still the same blinking light. So I called Atwood and they had me change the sail switch still the same problem so they said it was the board so I changed the board same problem. I talked to a rv tech and he said check the limit switch again by hooking the limit switch two white wires together and bypassing the switch the furnace runs then it is the switch. You can test for power on either side where the white wires connect also the sail switch will give you the same blinking light good luck

[Bird_Freak]

Flame is sensed thru the igniter wire. Check your wire connections for corrosion.
Mine did the same thing and it is likely the control board. Replace with a Dinosaur board instead of atwood.