Carrier 69NT40-541-505, Operation And Service Manual, Page: 66 / 143

T-368 4–36
AL54 PRIMARY SUPPLY SENSOR (STS)
Cause: Invalid Supply Temperature Sensor (STS) reading.
Component Supply Temperature Sensor (STS)
Troubleshooting Perform Pre-trip P5:
Corrective Action If P5 passes, no further action is required.
If P5 fails, replace the defective sensor as determined by P5, refer to TEM-
PERATURE SENSOR Service
Section 7.21 .
AL56 PRIMARY RETURN SENSOR (RTS)
Cause: Invalid Return Temperature Sensor (RTS) reading.
Component Return Temperature Sensor (RTS)
Troubleshooting Perform Pre-trip P5:
Corrective Action If P5 passes, no further action is required.
If P5 fails, replace the defective sensor as determined by P5, refer to TEM-
PERATURE SENSOR Service
Section 7.21 .
AL57 AMBIENT SENSOR (AMBS)
Cause: Invalid Ambient Temperature Sensor (AMBS) reading.
Component Ambient Temperature Sensor (AMBS)
Troubleshooting Test the AMBS, refer to TEMPERATURE SENSOR Service Section 7.21 .
Corrective Action Replace AMBS if defective, refer to TEMPERATURE SENSOR Service
Section 7.21 .
AL58 COMPRESSOR HIGH PRESSURE SAFETY (HPS)
Cause: High pressure safety switch remains open for at least one minute.
Component High Pressure Switch (HPS)
Troubleshooting Test the HPS; refer to High Pressure Switch, Section 7.9 .
Corrective Action Replace HPS if defective, refer to High Pressure Switch, Section 7.9 .
Component Refrigeration System
Troubleshooting Check unit for air flow restrictions.
Corrective Action Clean or remove any debris from coils.
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