Hi,

My furnace starts fan, pressure switches activate, gas valve turns on, but ceramic ignitor is not glowing. I changed the ignitor and no improvement. I measured the voltage on the plug with the ignitor disconnect during startup and only got 8 volts AC. Does this indicate that the control board needs to be replaced? Is there any other possibilities. The code is a 34.

Thanks

Code 34 = Ignition Proving Failure. If you look on the inside of the blower compartment door the code should be there on the wiring diagram.

You might try to clean the flame sensor with steel wool or sand paper.

Thanks for your input. The photos are very helpful.