Normal RPM of fan motor
Clean air filter
Refrigerant leaks
Frost blocks air circulation
Repair heater
Readjust the heater
Replace heater and bimetal thermo
Reuse the heater and over load protector
Non condensable gases
Moisture and wax from oil
Solid particles
Over charging of refrigerant
Under charge of refrigerant
Over charge of refrigerant
Defective fan motor
Defective timer
Open door switch
High watt Cabinet bulb