Arrived at house and owner only wanted me to check furnace out and not ac. Popped open furnace doors and called for heat. I got a motherboard error code of pressure switch failure to close. I do not have a pressure switch on hand. I will go over prices with owner and see if they'd like to continue so I can order part. Piece should work but if I install and system doesn't turn on. There could be other things wrong due to age of system. I cleaned out the pressure switch hose. I cleaned out ports with a thermostat wire. Pressure switch is stuck and won't let system turn on. Could be a blockage somewhere as well. Today charging for diagnostic only.