Thermo King 098916, Maintenance Manual

Page: 175 / 196

Diagnosis: Troubleshooting, Status Messages, Alarm Codes
174
27 Heat Capacity Test Error
(Check Alarm)
• Occurs during pretrip (PTI) test only.
• Difference between supply and return air
temperature is too small with high speed
evaporator fans (less than 0.4 C [0.7 F]).
• Indicates:
• Incorrect location of supply or return air sensor
• Air leakage at supply, return or evaporator coil
sensor cable
• Defective supply or return air sensor
• Interchanged sensor connections
• Defective heater elements
• Incorrect evaporator fan rotation or high speed
operation
• Container/side panels defective, damaged or
leaking
• Enter Manual Function Test and start
evaporator fans on high speed. Then select
Sensor Checks test and operate fans 2 to 5
minutes. Check supply, return and evaporator
coil (defrost) sensor temperatures. Sensor
readings should be the same (evaporator coil
may be 0.5 C [1.0 F] lower due to fan motor
heat).
NOTE: This sensor check does not detect
air leakage around the sensor cables.
• Open evaporator door and inspect evaporator
fan rotation. Make sure fans are rotating
correctly on high speed.
• Check the sensor connections.
28 Scroll Compressor, Low Pressure Indicates:
• Low pressure has occur from suction transducer
sensor
• Possible causes include low refrigerant charge,
defective pressure transducer, blocked TXV or
suction line restriction etc.
• Controller activates Alarm Code 31 after 5 min
• Controller clears message after compressor
start-up
31 Low Pressure Cutout Error
(Check Alarm)
• Occurs during pretrip (PTI) test only.
• Indicates:
• Low refrigerant charge
• Refrigeration system restriction at filter drier or
expansion valve
• Defective low pressure cutout switch
• Check discharge and suction pressure gauge
readings:
• If refrigerant pressures are low, check for a
restriction and leak check the refrigeration
system.
• If refrigerant pressures are high, check for a
high refrigerant charge (see below).
• Check for a restriction:
• Check for frost on down stream side of the
filter drier.
• Check for high evaporator superheat using
supply air sensor temperature readings in
Data menu or a frost pattern on expansion
valve side of the evaporator coil. A large
temperature difference between the left
hand and right hand supply air sensors
indicates a possible evaporator restriction or
incorrect superheat.
• Continuity check low pressure cutout switch
wiring using a high quality multimeter. Replace
switch.
Alarm Codes, Descriptions and Corrective Actions (Continued)
Code Description Corrective Action