Hello, i'm currently trying to fix my furnace. the board is telling me that the pressure switch is stuck open. I've gone and checked my flu pipe to see if anything was blocking it and i could only see about 7ft till the pipe turned and it was clear. I've also checked to see if the pressure switch hoses were cleared of anything and they where. I've gone and checked to see if the pressure switch and you can hear the switch clicking. I've also pulled of the inducer to see if their was a hard spot in the motor and its spinning as if it was brand new. At this point i'm lost and not sure whats to do. I'm not to sure if the inducer is pulling a good enough vacuum on the pressure switch but not to sure how to check that. Its a york 2 pipe 90% its about 6 years old Model Number is PC9C20N100UP11A and Serial #WOE6318492. Any help in the right direction would be appreciated thank you.