When I arrived at unit, I was told upstairs didn’t heat. I was here last week for a maintenance. My motherboard error code told me that the pressure switch is either open or closed. I cleared tubing of all dirt and debris. I used thermostat wire to clear ports on each end. I sucked the pressure switch to get to work. System kept turning on and shutting off. I took off molex plug and put in back into motherboard. I noticed three fry burns on motherboard and I recommended a new one to owner. He gave me permission to go ahead and order new one. Today just charging for diagnostic and will return for motherboard installation.