Upon arrival, the system was experiencing frequent shutdowns due to a pressure switch issue, leading to a system lockout from improper exhaust gas termination. I inspected the intake pipe, finding no issues, then examined the exhaust pipe, discovering water buildup. I adjusted the exhaust pipe pitch, cleared the hoses, and checked the secondary heating exchanger for blockages. Although no other faults were found, the system exhibited significant rust, which was noted for future maintenance.