7  06/11  Rev. B  127717 
MAINTENANCE SERVICE AND ANALY SIS GUIDE
REFRIGERATION SYSTEMS - ALL MODELS 
MALFUNCTION  POSSIBLE CAUSE  SOLUTION 
Compressor will not start -   1.  Service cord unplugged  1.  Plug in service cord  
no hum  2.  Fuse blown or removed  2.  Replace fuse 
  3.  Overload tripped  3.  Determine reasons and correct 
  4.  Control stuck open  4.  Repair or replace 
  5.  Wiring incorrect  5.  Check wiring against the diagram 
Compressor will not start -  1.  Improperly wired  1.  Check wiring against the diagram  
hums but trips on overload  2.  Low voltage to unit  2.  Determine reason and correct  
protector  3.  Starting capacitor defective  3.  Determine reason and replace 
  4.  Relay failing to close  4.  Determine reason, correct or replace   
Compressor starts and runs,  1.  Low voltage to unit  1.  Determine reason and correct  
but short cycles on overload  2.  Overload defective  2.  Check current, replace overload protector  
protector  3.  Excessive head pressure  3.  Check ventilation or restriction in     
       refrigeration system 
  4.  Compressor hot-return gas hot  4.  Check refrigerant charge, fix leak if necessary 
Compressor operates long  1.  Short of refrigerant  1.  Fix leak, add charge  
or continuously  2.  Control contact stuck  2.  Repair or replace 
  3.  Evaporator coil iced  3.  Determine cause, defrost manually 
  4.  Restriction in refrigeration system  4.  Determine location and remove restriction  
  5.  Dirty condenser  5.  Clean condenser 
Compressor runs fine, but  1.  Overload protector  1.  Check wiring diagram  
short cycles  2.  Cold control  2.  Differential too close - widen 
  3.  Overcharge  3.  Reduce charge 
  4.  Air in system  4.  Purge and recharge 
  5.  Undercharge  5.  Fix leak, add refrigerant 
Starting capacitor open,  1. Relay contacts stuck  1.  Clean contacts or replace relay  
shorted or blown  2.  Low voltage to unit  2.  Determine reason and correct 
  3.  Improper relay  3.  Replace 
Relay defective or burned out  1.  Incorrect relay  1.  Check and replace 
  2.  Voltage too high or too low  2.  Determine reason and correct 
Refrigerated space too warm  1.  Control setting too high  1.  Reset control 
  2.  Refrigerant overcharge  2.  Purge refrigerant 
  3.  Dirty condenser  3.  Clean condenser 
  4.  Evaporator coil iced  4.  Determine reason and defrost 
  5.  Not operating  5.  Determine reason, replace if necessary 
Standard temperature system  1.  Control setting is too low  1.  Reset the control  
freezes the product  2.  Control points stuck  2.  Replace the control 
Objectionable noise  1.  Fan blade hitting fan shroud  1.  Reform or cut away small section of shroud 
  2.  Tubing rattle  2.  Locate and reform 
  3.  Vibrating fan blade  3.  Replace fan blade 
  4.  Condenser fan motor rattles  4.  Check motor bracket mounting, tighten 
  5.  General vibration  5.  Compressor suspension bolts not loosened 
    on applicable models - loosen them 
  6.  Worn fan motor bearings  6.  Replace fan motor 
Pan Area  1.  No cooling  1.  Make sure switch is in the "on" position 
  2.  Too cold  2.  Adjust temperature control - see instructions 
      under pan area 
  3.  Too warm  3.  Adjust temperature control - see instructions 
      under pan area