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© 2012 Mobile Climate Control T-299 Rev. 08/2012
Table 3-4 GENERAL SYSTEM TROUBLESHOOTING PROCEDURES
INDICATION/
TROUBLE
POSSIBLE CAUSES
3.2 SYSTEM WILL NOT COOL
Compressor will not run Drive--Belt loose or defective
Clutch coil defective
Clutch malfunction
Low refrigerant charge
Compressor malfunction
Electrical Malfunction Circuit Breaker Open
Relay Defective
3.3 SYSTEM RUNS BUT HAS INSUFFICIENT COOLING
Compressor Drive--Belt loose or defective
Compressor defective
Refrigeration system Abnormal pressures
No or restricted evaporator air flow
Expansion valve malfunction
Restricted refrigerant flow
Low refrigerant charge
3.4 ABNORMAL PRESSURES
High discharge pressure Refrigerant overcharge
Noncondensables in system
Condenser motor(s) failure
Dirty Condenser coil
Skirt--Mounted Condenser recirculating hot air from under bus.
Low discharge pressure Compressor defective
Low refrigerant charge
High suction pressure Compressor defective
Low suction pressure Filter---drier or Receiver---D rier partially plugged
Low refrigerant charge
Expansion valve malfunction
Restricted air flow
Suction and discharge pressures
equal or near equal
Compressor valves defective
3.5 ABNORMAL NOISES, VIBRATIONS OR CONDITIONS
Compressor -- Engine area Compressor or compressor mounting loose
Liquid slugging
Insufficient oil
Excessive oil
Clutch loose, rubbing or defective
Dirt or debris on vehicle fan blades
Drive belt cracked, worn or loose
Evaporator area Evaporator blower assembly broken or loose
Blower wheel loose or out of alignment
Blade interference
Condenser area Broken or missing fan blade
Condenser assembly loose
Fan assembly loose
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