Checked all operations in the heating mode and inspected the furnace filter. Checked all operations in the heating mode and inspected the furnace filter. Checked all electrical components and preformed a combustion analysis of the furnace. Furnace was burning fuel properly and all electrical components were within factory specifications. Today I talked with customer about a better filter to help protect the system and improve air quality. Customer is holding off on having the electrostatic filter installed. System is operating properly at this time.