was on a call today and ran across a stuck open pressure switch fault on a york furnace. 90% 80,000 btu upflow modulating natural gas furnace.
was able to unstick pressure switch and is working fine now. i found a couple of droplets of condensation at pressure switch port and in tubing. this is the pressure switch off of inducer motor and not the one tat goes to the secondary heat exchanger cover. even though everything is working now i have a feeling that the same problem will result.
thanks for your help.