Thermo King CRR-40 119, Manual

Page: 156 / 170

Diagnosis
156
Frosted or sweating suction
line Expansion valve admitting excess
refrigerant Check feeler bulb and adjust expansion
valve
Evaporator coil needs defrosting Check defrost circuit including controller
and evaporator coil sensor
Evaporator fan does not operate See “Evaporator fan motor does not
operate” under Mechanical Diagnosis
Unit in vacuum. Frost on
expansion valve only Ice plugging expansion valve screen
or orifice Apply hot wet cloth to expansion valve.
Moisture indicated by increase in suction
pressure. Replace filter drier
High suction pressure Overcharge of refrigerant Purge system
Expansion valve open too much Adjust or replace valve
Defective controller or main relay
board Diagnose main relay board and
controller. Replace defective component
Suction pressure gauge out of
calibration Adjust or replace service gauge
Low suction pressure
NOTE: This unit has a
suction modulation
capacity control system.
Suction and discharge
pressures may drop below
expected normal readings
when the unit is on
Modulation Cool (control
temperature within 10 C
[18 F] of setpoint or in
Power Limit mode).
Shortage of refrigerant Repair leak and recharge
Low ambient air temperature No remedy
Iced or dirty evaporator coil Defrost or clean evaporator coil
Restricted lines Locate and clear restriction
Plugged filter drier Replace filter drier
Expansion valve closed too much Adjust or replace valve
Expansion valve feeler bulb
improperly mounted, poorly insulated
or making poor contact Correct feeler bulb installation
Evaporator fans off Check evaporator fan motors and
control circuit and correct fault
Defective controller or main relay
board Diagnose main relay board and
controller. Replace defective component
Suction pressure gauge out of
calibration Adjust or replace gauge