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Hi my name is ***** ***** I'm here to help you out! If the control module is intermittently putting out random voltages then it is failing. To triple check, remove the wires to the gas valve (when the unit decides when it doesn't want to work again - and it will) and measure voltage. This will confirm the gas valve is not intermittently causing an issue. Very rarely is this the case, but it can happen. I've seen many failing controllers on pulses do exactly what you are describing here.
Okay, is this a g14 or g21 pulse? Is the light on the control module "on" when trying to light? Can you hear the inducer "surging" (on....off....on...off)?
Also did you remove the wires from the gas valve and see if you were getting voltage to those wires while trying to light?
The pressure switch is a normally closed switch - if there is a draft blockage, the switch will open and drop control voltage. If the switch opens (has no continuity) then the inducer will not run or surge. The surging will be apparent. This is the opposite of most furnace pressure switches that prove draft. This switch proves a blockage.
Reading your last post I think I see the mix up - the board in question was the ignition module, not the fan timer board. The ignition module sends 24v to the gas valve to open... This is the board I was referring to originally. You stated control module and I was interpreting that as the ignition module.
I'm sorry for the mix up- it's a little challenging to troubleshoot with this method so we do our best!
Yes the common to the gas valve comes from the fan timer board, but the 24 volt hot comes from the ignition module.