colman heater won't light up

[fordfixer]

I have a Colman Evcon furance the heating element gets hot and when the gas comes on it trys to light but clicks off.The heating element will reheat and the gas will try again but will kick off and the fan is running all the time.any idea what might be causing the gas to turn off?

[JCA1]

Check the gas valve for 24v when you hear the control board click. If no current at the valve check it directly on the control, if no current there replace the control board.( you can try tapping the control board lightly beofre it signals the valve, this might work but might not)

[JCA1]

Wait, do you mean that the gas actually lights and then goes off? If so try cleaning/replacing the flame sensor.

[fordfixer]

yes the gas will light for gust a second and then clicks off,and yes i have 24 volts at the gas valve and the controll board.

[JCA1]

You should see a single wire( probably yellow) exiting the burner assemble with the ignitor wires(2) going to the "sense"( maybe called something else, I can't remember) connector on the control board, Remove the burner assembly and clean the rod at the end of this wire and see if that works. If not, using a piece of lite guage stiff wire, replicate this sensor and connect it to the board and see if it works, if so replace the sensor/assembly. The sensor is not letting the control know the flame is burning or the control is bad and not recieving the signal. If you do not have this sensor on your model let us know.

[fordfixer]

i have two white wires going to the ignitor but no wires other than that,it looks like i have 3 flat sensors 2 above the ignitor and 1 below the modle number is cgu08016 any ideas?thanks.

[HayZee518]

that thing they're looking for is called a flame rod. it is a stainless steel rod with a definite resistance. applying a flame reduces the resistance and allows the control to sense a flame before opening the main valve.

[fordfixer]

i do have a rod connected under the ignitor but it has no wires or connectors of and kind would this be the rod and if so how would you check ohms?

[HayZee518]

ok, no wires would indicate a mechanical pilot flame detector. this is a cappillary tube with a gas inside that expands when heated. it drives a bellows inside the main valve to open the main valve. if the gas leaked out there would be no flame detection.

[fordfixer]

so what would be the next move on this repair?