Performed a two system maintenance checking the heat, checked all electrical and mechanical components and all safety switches, cleaned flame sensors, checked systems operation, and amp draws, everything is working properly at this time, homeowner did mention that the upstairs a/c wasn’t working well. While up in the attic opened up coil and found oil on the manifold for coil. Checked pressures outside and found system almost empty of refrigerant. Emailed estimate to replace coil under warranty, homeowner wanted to hold off till next spring and be reminded next time to see if he still wants to replace evaporator coil for upstairs, noted that labor price may change next year.