Performed 3 heating maintenances on 2017 gas systems. We checked amps, capacitors, filters, electrical, cleanliness, and safeties. The systems are heating inside of manufacture specifications. However, we noticed that one of the gas valves is becoming compromised. We advise replacing it before failure/gas leak occurs. We observed that none of the outdoor units have surge protection. These serve as a safety net for the compressor. We performed a dryer vent cleaning during the time of service. Customer approved 2 stage white rogers