Furnace & AC Tune Up Procedure Checklist:

Inspect and clean blower assembly(includes blower housing, blower wheel and motor).
On older models, lubricate motor and inspect and replace fan belt if needed.
Check combustion blower housing for lint and debris and clean as necessary
Inspect evaporator coil, drain pan and condensate drain lines. Clean as needed.
Inspect for gas leaks in gas furnaces.
Inspect burner assembly -- clean and adjust as needed.
Inspect ignition system and safety controls -- clean and adjust as needed.
Inspect heat exchanger or heating elements.
Inspect flue system -- check for proper attachment to the furnace, any dislocated sections, and for signs of corrosion. Replace if necessary.
Inspect control box, associated controls, wiring and connections.
Clean or replace air filters.
Inspect conditioned airflow system(ductwork) -- check for leaks.

Inspect unit for proper refrigerant level and adjust if necessary
Clean dirt, leaves and debris from inside cabinet
Inspect bas pan for restricted drain openings - remove obstructions as necessary
Inspect coil and cabinet - clean as needed
Inspect fan motor and fan blades for wear and damage - on older models lubricate as needed
Inspect control box. associated controls/accessories. wiring and connections. Controls may include contactors, relays, circuit boards, capacitors, sump heat and other accessories. All control boxes and electrical parts should be checked for wear or damage.
Inspect compressor and associated tubing for damage.

Monitor system starting characteristics and capabilities.
Listen for abnormal noise
Search for source of unusual odors.
Monitor air conditioning and heat pumps systems for correct refrigerant charge
Measure outdoor dry bulb temperature.
Measure indoor dry and wet bulb temperatures
Measure high and low side system pressures
Monitor gas furnace for correct line and manifold gas pressure -- make adjustments as needed.
Measure temperature rise and adjust airflow as needed
Check vent system for proper operation
Monitor system for correct line and load volts/amps.
Monitor system operation per manufacturer's specification
Provide system operation report and recommend repairs or replacement as necessary