When I arrived at unit, the package unit didn’t work In heating mode. I set thermostat to heat and went out to unit. Unit only had exhaust running in system. I looked up error code on motherboard and it directed me towards pressure switch fault. Pressure switch needed to be disconnected. Checked for continuity. Took off pressure tube hose and blew out all debris out of tubing. Then I cleared out tube port on each end. After diagnosing pressure switch. I put disconnect back in and system fired off In heating mode. System is operational upon departure.