65
WARNING:
Disconnect all power to unit before servicing. Contactor may break only one side.
Failure to shut off power can cause electrical shock resulting in personal injury or death.
SYMPTOM
POSSIBLE CAUSE
REMEDY
Unit will not run
• Power off or loose electrical connection
• Thermostat set too high or low.
• Unit in active compresor protection
•
lockout mode
• Blown fuses/tripped breaker
• Transformer defective
• High-pressure control open
• Miswiring of communications (communication
light on continuously)
• Defective control board
• Check for correct voltage at line voltage connections in
condensing unit.
• Reset – Power cycle high and low voltage to outdoor
•
unit
• Check control board diagnostic codes.
• Replace fuses/reset breaker.
• Check wiring. Replace transformer.
• Reset. Also see high head pressure remedy. The high-
pressure control opens at 610 PSIG [420 kPa].
• Check communication wiring.
Outdoor fan runs,
compressor doesn't
• Loose connection
• Communication cable disconnected or failed
• Compressor stuck, grounded or open motor
winding, open internal overload.
• Low-voltage condition
• Check for correct voltage at filter and inverter. Check
and tighten all connections.
• Check control board diagnostic codes.
• Replace
Insufficient cooling
• Improperly sized unit
• Improper indoor airflow
• Incorrect refrigerant charge
• Air, noncondensibles, or moisture in system
• Restricted Refrigerant Circuit
• Recalculate load.
• Check airflow. Should be approximately 400 CFM per
ton.
• Charge per procedure attached to unit service panel.
• Recover refrigerant. Evacuate and recharge.
Replace filter drier.
Compressor short
cycles
• Incorrect voltage
• Improperly sized unit
• Refrigerant undercharge
• At inverter input terminals, voltage must be between
187-252VAC when unit is operating.
• Add refrigerant.
Registers sweat
• Low indoor airflow
• Increase speed of blower or reduce restriction.
Replace air filter.
High head, low vapor
pressures
• Restriction in liquid line, expansion device, or
filter drier
• Stuck EXV
• Remove or replace defective component.
• Verify EXV operation.
High head, high
or normal vapor
pressure – Cooling
mode
• Dirty outdoor coil
• Refrigerant overcharge
• Outdoor fan not running
• Air or noncondensibles in system
• Clean coil.
• Correct system charge.
• Repair or replace.
• Recover refrigerant. Evacuate and recharge.
Low head, high vapor
pressures
• EXV in bypass mode
• Reversing Valve leaking by
• Bad compressor
• Verify thermostat connections at EXV control
• Verify thermister and pressure transducer connection
and operation
• Replace compressor.
Low vapor, cool
compressor, iced
indoor coil
• Low indoor airflow
• Operating below 55°F outdoors
• Moisture in system
• Low ambient cooling not operating (coil or
ambient thermister failure)
• Increase speed of blower or reduce restriction.
Replace air filter.
• Recover refrigerant. Evacuate and recharge. Replace
filter drier.
High vapor pressure
• Excessive load
• Defective compressor
• Recheck load calculation.
• Replace compressor.
Fluctuating head and
vapor pressures
• EXV hunting
• Air or noncondensibles in system
• Check thermistor to vapor line connection. Check air
distribution on coil.
• Check suction thermistor and pressure transducer
operation
• Recover refrigerant. Evacuate and recharge.
• Remove & confirm EXV movement. Clean EXV inside
with nitrogen to remove any debris then reinstall
Gurgle or pulsing
noise at expansion
device or liquid line
• Air or noncondensibles in system
• Undercharge long line application
• Recover refrigerant. Evacuate and recharge.
9.11 General Troubleshooting Guide
Diagnostics
9.0 DIAGNOSTICS & TROUBLESHOOTING
