4–43
T-372
AL253
Battery Pack Fault
Cause:
Any of the USDA1, USDA2, or USDA3 probes have been detected AND the Backup Battery Test
Result is Failure. Or, no Battery.
Component
Battery
Troubleshooting
Perform battery test in function code Cd19 to determine failure mode of
battery.
Corrective Action
To clear the alarm, replace the battery pack. See
Replacement. If after replacement the alarm continues, run Cd19 to
determine whether the replaced battery is good.
AL254
Primary Supply Temperature Sensor (STS) Fault
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. See Temperature Sensor Service
AL256
Primary Return Temperature Sensor (RTS) Fault
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. See
AL257
Ambient Sensor (AMBS) Fault
Cause:
Invalid Ambient Temperature Sensor (AMBS) reading.
Component
Ambient Temperature Sensor (AMBS)
Troubleshooting
Test the AMBS. See Sensor Checkout Procedure
.
Corrective Action
Replace AMBS if defective. See Temperature Sensor Service
AL258
Compressor High Pressure Safety Open
Cause:
High pressure safety switch remains open for at least one minute.
Component
High Pressure Switch (HPS)
Troubleshooting
Test the HPS. See Checking High Pressure Switch,
.
Corrective Action
Replace HPS if defective. See Sensor Replacement,
.
Component
Refrigeration System
Troubleshooting
Check unit for air flow restrictions.
Corrective Action
Clean or remove any debris from coils.