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TABLE 3 – REFRIGERATION SYSTEM SERVICE AND ANALYSIS CHART
REFRIGERATION SYSTEM
MALFUNCTION
POSSIBLE CAUSE
SOLUTION
1. Line cord not plugged in.
1. Plug in the cord.
2. Fuse removed or blown.
2. Replace fuse.
3. Overload protector tripped.
3. Refer to electrical section.
4. Temp control stuck in open position.
4. Repair or replace temp control.
Compressor will not start
- no hum -
5. Wiring improper or loose.
5. Check wiring against diagram.
1. Low voltage to unit.
1. Determine reason and correct.
2. Relay failing to close
2. Determine reason and correct, replace if
necessary.
3. Starting capacitor defective.
3. Determine reason and replace.
Compressor will not start
- hums but trips on overload
protector.
4. Improperly wired.
4. Check wiring against diagram.
1. Low voltage to unit.
1. Determine reason and correct.
2. Relay failing to open.
2. Determine reason and correct, replace if
necessary.
3. Run capacitor defective.
3. Determine reason and replace.
Compressor starts but does not
switch off of start winding.
4. Compressor mounting winding is open or
shorted.
4. Determine cause, correct, and replace
compressor.
1. Additional current passing through overload
protector.
1. Check wiring diagram. Check for added fan
motors, pumps, etc. connected to wrong side of
protector.
2. Low voltage to unit.
2. Determine reason and correct.
3. Overload protector defective.
3. Check current, replace protector.
4. Run capacitor defective.
4. Determine reason and replace.
5. Excessive discharge pressure.
5. Check ventilation, restrictions in cooling medium,
restrictions in refrigeration system.
Compressor starts and
runs, but short cycles on
overload protector.
6. Compressor too hot - return gas hot.
6. Check refrigerant charge (fix leak if necessary).
Check airflow across condenser.
1. Overload protector.
1. Check wiring diagram for correct wiring.
2. Cold control.
2. Differential set too close.
3. Overcharge.
3. Reduce refrigerant charge.
4. Air in system.
4. Recover and recharge.
Unit runs OK, but short
cycles.
5. Undercharge.
5. Fix leak and recharge with refrigerant.
1. Dirty condenser.
1. Clean condenser.
2. Shortage of refrigerant.
2. Fix leak, add charge, correct charge.
3. Temperature control contacts stuck or frozen.
3. Replace temperature control.
4. Evaporator coil iced.
4. Defrost.
Unit operates long or
continuously.
5. Restriction in refrigeration system.
5. Determine location and remove.
1. Relay contacts not opening properly.
1. Replace relay.
2. Low voltage to unit.
2. Determine reason and correct.
Start capacitor open, shorted or
blown.
3. Improper relay.
3. Replace.
1. Improper capacitor.
1. Determine correct size and replace.
Run capacitor open, shorted
or blown
2. Excessively high line voltage (110% of rated
max).
2. Determine reason and correct.
1. Incorrect relay.
1. Check and replace.
2. Line voltage too high or too low.
2. Determine reason and replace.
Relay defective or burned out
3. Relay being influenced by loose vibrating
mounting.
3. Remount rigidly.
1. Control setting too high.
1. Reset control.
2. Overcharged with refrigerant.
2. Recover refrigerant and recharge with proper
charge specified on data plate.
Space temperature too high
3. Inadequate air circulation.
3. Improve air movement.
Cooler freezing beverage
1. Temperature control
1. Reset control.
1. Loose parts or mountings.
1. Find and tighten.
2. Tubing rattles.
2. Reform to be free of contact.
3. Bent fan blade causing vibration.
3. Replace blade.
Unit noisy
4. Fan motor bearings worn.
4. Replace motor.
