Came out to perform preventative maintenance on furnaces for customer. Discussed with customer about filters, the holidays, and how things have been going. Customer takes care of the filters in home. I inspected the ductwork, blower assemblies, electrical components, heat exchangers, burners, flame sensors, ignitors, gas valves, inducer motors and overall condition of all equipment. Cleaned flame sensors and brushed dust off the burners and components. Checked operation, wiring, capacitors, amps, temperature rise and gas pressure of furnaces. The 20+ year old trane furnace is still functioning and holding up. Systems are heating properly within manufactured specifications at this time.