Ingersoll-Rand Thermo King CRR DF MPC2000, Maintenance Manual

Page: 94 / 165

Microprocessor Controller
93
34 Ambient Air Sensor Open Circuit
(Check Alarm)
• Sensor circuit resistance is higher than 100,000
ohms.
• Temperature is below -70 C (-94 F).
• Indicates:
• Open circuit to sensor
• Defective or wrong sensor
• Defective relay board
• Defective cable No. 1
• Defective controller
• Check sensor resistance between pins 13 and
14 on plug J15. Resistance must be 1,000
ohms at 25 C (77 F).
• Check cable No. 1 between controller and relay
board.
35 Ambient Air Sensor Short Circuit
(Check Alarm)
• Sensor circuit resistance is lower than 200
ohms.
• Temperature is above 80 C (176 F).
• Indicates:
• Short circuit to sensor
• Defective or wrong sensor
• Defective relay board
• Defective cable No. 1
• Defective controller
• Check sensor resistance between pins 13 and
14 on plug J15. Resistance must be 1,000
ohms at 25 C (77 F).
• Check cable No. 1 between controller and relay
board.
43 Return Air Temperature Too High
(Check Alarm)
• Return air temperature increases above 35 C
(95 F) during defrost.
• Indicates:
• Defective return air or evaporator coil sensor
• Return air and evaporator coil sensor
connections are reversed
• Check for sensor alarm codes.
• Check supply and return sensor connections
and locations.
52 • Probe Error
(Check Alarm)
• Occurs during Pretrip (PTI) test only.
• Temperature difference between supply air,•
return air or evaporator coil sensor is too high (3
C maximum)
• Indicates:
• Indication error on one of the sensors
• Supply air sensor not placed in airflow stream
• Check sensor connections. Check sensor
resistance of each sensor. Resistance must be
1,000 ohms at 25 C (77 F).
• Check supply air sensor locations.
Code Description Corrective Action