I have an Atwood 8531 furnance in my trailer and I just replaced the circuit board because it was bad. I am still not getting ignition when the unit comes on. What is the voltage supposed to be to the ignition probe? I am only getting between 7 and 9 volts. I am getting gas but it will not ignite.
I am wondering why you replaced the circuit board? If you are measuring the voltage to the spark probe when it fires very low as the service manual lists that as a "high tension" lead and does not specify a voltage but it is in the 1000V or so range. They do advice not to attempt to measure it.
I suggest that you download a copy of the service manual from the site of Bryant RV and study it.