15
TROUBLESHOOTING CHART
Symptom
Possible Cause
Remedy
High head—
low suction
■
Restriction in liquid line or flowrator
■
Remove or replace with proper size flowrator.
High head—
high or normal
suction
■
Dirty condenser coil
■
Overcharged
■
Condenser fan not running
■
Clean coil.
■
Correct system charge.
■
Repair or replace condenser fan.
Low head—
high suction
■
Incorrect flowrator
■
Defective compressor valves
■
Flowrator not seating properly
■
Replace with correct flowrator.
■
Replace compressor.
■
Check for debris under flowrator or deformed flowrator. Remove debris
or replace flowrator.
Unit will not
run.
■
Power off or loose electrical connection
■
Thermostat out of calibration; set too
high
■
Defective contactor
■
Blown fuses or tripped circuit breaker
■
Transformer defective
■
High or low pressure control (optional)
open
■
Compressor overload contacts open
■
Check for unit voltage at contactor in unit.
■
Reset thermostat.
■
Check for 24 volts at contactor coil. Replace if contacts are open.
■
Replace fuse or reset circuit breaker. Check wiring. Replace
transformer.
■
Reset high pressure control or check unit charge.
High pressure control opens at 610 psig, and low pressure control
opens at 22 psig.
■
Replace compressor.
NOTE: Wait at least 2 hours for overload to reset.
Condenser fan
runs;
compressor
does not run.
■
Loose connection
■
Compressor stuck
■
Grounded or open winding
■
Open internal overload
■
Low voltage connection
■
Capacitor weak, open or shorted
■
Check for unit voltage at compressor.
■
Check and tighten all connections.
■
Wait at least 2 hours for overload to reset. If still open, replace the
compressor.
■
At compressor terminals, voltage must be within 10% of nameplate
volts when unit is operating.
■
Check capacitor. Replace if defective.
Low suction—
cool
compressor,
iced
evaporator coil
■
Low indoor airflow
■
Increase speed of blower or reduce restriction.
■
Replace air filters.
Compressor
short cycles
■
Defective overload protector
■
Unit cycling on low pressure control
■
Replace overload protector. Check for correct voltage.
■
Check refrigerant charge and/or airflow.
Registers
sweat
■
Low airflow
■
Increase speed of blower or reduce restriction.
■
Replace air filters.
High suction
pressure
■
Excessive load
■
Defective compressor
■
Reversing valve not seating properly.
■
Recheck load calculation
■
Replace compressor.
■
Replace reversing valve.
Insufficient
cooling
■
Improperly sized unit
■
Improper airflow
■
Incorrect refrigerant charge.
■
Incorrect voltage
■
Recalculate load.
■
Check airflow—should be approximately 400 CFM per ton.
■
Charge per procedure attached to unit service panel.
■
At compressor terminals, voltage must be within 10% of nameplate
volts when unit is operating.
Evaporator
coil freezing or
frosting
■
Low airflow
■
Low refrigerant charge
■
Operating unit in cooling mode below
65ºF (18ºC) outdoor temperature
■
Check airflow—should be approximately 400 CFM per ton.
■
Properly charge unit.
■
Install or check low ambient control—should be open below 65ºF
(18ºC) outdoor temperature.
HIGH VOLTAGE!
WARNING
Disconnect ALL power before servicing.
Multiple power sources may be present.
Failure to do so may cause property damage, personal injury or death.
