Test for carbon monoxide leaks Inspect heat exchenger (for any cracks or pinholes)
Test and check motor and fan condition Inspect & adjust burners (make sure flame is the right height and color)
Test gas pilot safety system Check electrical control wiring (to see if any burnt, or bare wires and loose connections)
Check for proper air requirements (Air to gas ratio, for optimal savings on gas bill) Check power vent system
Check vent damper operation Check pulleys & shaft
Check door switch Clean & inspect thermostat
Check blower operation Inspect filter & electronic air cleaner
Check gas piping for leaks Examine flue & vent connectors
Check ventor blower operation Test spark ignition
Check pressure switch Check spillage
Inspect igniter Test operation of limit controls
Check fan belt & adjust if needed (make sure not worn, cracked or frayed, and not on too loose or too tight) Lubricate fan & motor bearings
Check & clean pilot Check combustion & ventilation
Test pressure switches Check condition of vented system
Check condensate line condition Check roll out switch
Check safety controls Check temperature rise across heat exchenger