30
General Troubleshooting (continued)
Problem
Possible Cause
Remedy
Low
refrigerant
pressure
Low refrigerant charge
Contact refrigeration service technician
Refrigerant leak
Contact refrigeration service technician
Low flow through evaporator
Adjust flow to proper level
Clogged Y-strainer
Clean Y-strainer
Clogged evaporator
Back flush / clean evaporator
Expansion valve
Check start-up settings
Check control power to IB board, check fuse
Check control signal output from Microprocessor
Replace IB board if faulty
Replace expansion valve if faulty
Liquid line solenoid valve
Check Microprocessor output for control power
Check interface relay, replace if faulty
Check solenoid coil, replace if faulty
Liquid line service valve
Open valve
Compressor suction service valve
Open valve all the way
Low refrigerant pressure transducer
Replace if faulty
Microprocessor sensor input
Replace if faulty
High
refrigerant
pressure
Plugged condenser
Clean condenser
Insufficient condenser water flow (MXW models only) Check flow is in range
High condenser water temperature (MXW models
only)
Maximum temperature is 105°F
Condenser water regulating valve (MXW models only) Replace if faulty
High condenser air temperature (MXR models only)
Maximum temperature is 115°F
Condenser fans inoperable (MXR models only)
Check operation of all condenser fans
Compressor discharge service valve is not open fully Open valve all the way
Refrigerant circuit overcharged
Contact refrigeration service technician
High refrigerant pressure transducer
Replace if faulty
Microprocessor sensor input
Replace if faulty
Low
differential
pressure
Condenser overcooling
Check operation of WRV (MXW units)
Check operation of fans (MXW units)
Adjust discharge pressure set point
Discharge pressure set point
Increase discharge pressure set point
High suction pressure
Check operation of expansion valve
Max suction pressure is 55 psig
PLC sensor input, suction/discharge pressure
transducers
Replace if faulty
High oil
temperature
or high
discharge
temperature
Liquid injection
Check for proper operation
Oil temperature sensor
Replace if faulty
Discharge temperature sensor
Replace if faulty
Low oil level
Contact the Service Department for assistance
Microprocessor input card
Replace if faulty
