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Troubleshooting
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Table 23 Compressor and refrigeration system troubleshooting
Symptom Possible Cause Check or Remedy
Compressor will not
start
Power off Check main switch, fuses or CBs and wiring
Current overload open Reset manually
Loose electrical connections Tighten connections
Compressor motor burned out Check and replace compressor if defective.
Compressor will not
operate, contactor not
pulling in
No call for cooling Check monitor status.
Solenoid valve not energizing
Hold screwdriver over solenoid and check for magnetic field.
This indicates solenoid is energized.
Low pressure switch not making
contact
Check gas pressure - manually energize low pressure
switch.
Compressor will not
operate, contact not
pulling in
High pressure switch open
Reset switch. Refer to other refrigeration troubleshooting
suggestions.
Compressor contactor
pulled in but
compressor will not
operate
Blown fuse or tripped CB
Check for line voltage after fuses or CBs, and after
contactors.
Compressor runs for
three minutes then
stops; contactor drops
out. Motor operates but
valve won't open
Low pressure switch not closing
Check for low gas pressure. Compressor is running on
Positive Start Kit (air cooled systems only).
Solenoid not opening Check magnetic field to see if energized.
High discharge
pressure
Dirty condenser or drycooler fins Clean coil
Condenser equipment not
operating
Check operation.
High refrigerant charge Check refrigerant charge.
Hot gas bypass valve adjusted
improperly
Adjust properly.
Water regulating valve adjusted
improperly
Adjust properly.
Low discharge pressure
Excessive water now through
condenser
Adjust water regulating valve
Suction service valve partially
closed
Open the valve.
Leaky compressor suction valves
Pump down, remove the cylinder head, examine valves and
valve seats; replace if necessary
Worn piston rings Replace compressor.
Faulty head pressure control
valve or condenser fan speed
control
Replace if defective.
Low suction pressure
Insufficient refrigerant in system Check for leaks, repair, and add refrigerant
Dirty air filters Change filters.
Plugged filter-drier Replace filter.
Improper superheat adjustment Reset expansion valve for 10-15°F
Defective expansion valve
sensing element
Replace element
Poor air distribution
Check duct work for closed dampers. Check for underfloor
restrictions at or near the unit.
Low condensing pressure Check head pressure control device.
Slipping belts Inspect and adjust