Checking and cleaning the fan assembly (includes blower housing, fan wheel and motor)
On older models, Lubricate the engine and check and/or replace the fan belt if necessary
Inspect combustion blower housing for lint and debris and clean as necessary
Check the evaporator coil, drain pan and condensate drain lines. Cleaning.
Check for possible gas leaks in gas furnaces
Checking the burner assembly.
Check the control box, corresponding controls, wiring and connections
Clean or replace the air filter
Check the air conditioning system (duct) – check for leaks