11/12 150139 Rev. D
4
MAINTENANCE SERVICE AND ANALYSIS GUIDE
REFRIGERATION SYSTEMS - ALL MODELS
MALFUNCTION
POSSIBLE CAUSE SOLUTION
Compressor will not start - no hum 1. Unplugged or power off
2. Fuse blown or removed
3. Overload tripped
4. Control stuck open
5. Wiring incorrect
1. Plug in service cord or turn on power
2. Replace fuse
3. Determine reasons and correct
4. Repair or replace
5. Check wiring against the diagram
Compressor starts and runs, but short cycles on overload
protector
1. Improperly wired
2. Low voltage to unit
3. Starting capacitor defective
4. Relay failing to close
1. Check wiring against the diagram
2. Determine reason and correct
3. Determine reason and replace
4. Determine reason, correct or replace
Compressor will not start - hums but trips on overload
protector
1. Low voltage to unit
2. Overload defective
3. Excessive head pressure
4. Compressor hot -- warm ambient
1. Determine reason and correct
2. Check current, replace overload protector
3. Check ventilation or restriction in
refrigeration system
4. Check refrigerant charge, fix leak if
conditions necessary
Compressor operates long or continuously 1. Short of refrigerant
2. Control contact stuck
3. Evaporator coil iced
4. Restriction in refrigeration system
5. Dirty condenser
1. Fix leak, add charge
2. Repair or replace
3. Determine cause, defrost manually
4. Determine location and remove restriction
5. Clean condenser
Compressor runs fine, but short cycles 1. Overload protector
2. Cold control
3. Overcharge
4. Air in system
5. Undercharge
1. Check wiring diagram
2. Differential too close – widen
3. Reduce charge
4. Purge and recharge
5. Fix leak, add refrigerant
Starting capacitor open, shorted or blown 1. Relay contacts stuck
2. Low voltage to unit
3. Improper relay
1. Clean contacts or replace relay
2. Determine reason and correct
3. Replace
Relay defective or burned out 1. Incorrect relay
2. Voltage too high or too low
1. Check and replace
2. Determine reason and correct
Refrigerated space too warm 1. Control setting too high
2. Refrigerant overcharge
3. Dirty condenser
4. Evaporator coil iced
5. Not operating
6. Air flow to condenser or
7. Warm ambient conditions
1. Reset control
2. Purge refrigerant
3. Clean condenser
4. Determine reason and defrost
5. Determine reason, replace if necessary
6. Remove obstruction for free air flow – no
evaporator blocked storage on top of walk-in
7. Ambient conditions should be 90° or less
Standard temperature system freezes the product 1. Control setting is too low
2. Control points stuck
1. Reset the control
2. Replace the control
Objectionable noise 1. Fan blade hitting fan shroud
2. Tubing rattle
3. Vibrating fan blade
4. Condenser fan motor rattles
5. General vibration
6. Worn fan motor bearings
1. Reform or cut away small section of
shroud
2. Locate and reform
3. Replace fan blade
4. Check motor bracket mounting, tighten
5. Compressor suspension bolts not
loosened on applicable models - loosen
them
6. Replace fan motor
