T-362 4–38
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. See Temperature
Sensor Service Section 7.29.
AL57 Ambient Sensor (AMBS)
Cause: Invalid Ambient Temperature Sensor (AMBS) reading.
Component Ambient Temperature Sensor (AMBS)
Troubleshooting Test the AMBS. See Sensor Checkout Procedure Section 7.29.2.
Corrective Action Replace AMBS if defective. See Temperature Sensor Service Section 7.29.
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. See Checking High Pressure Switch, Section 7.10.1.
Corrective Action Replace HPS if defective. See Sensor Replacement, Section 7.29.
Component Refrigeration System
Troubleshooting Check unit for air flow restrictions.
Corrective Action Clean or remove any debris from coils.
AL59 Heater Termination Thermostat (HTT)
Cause: Heat Termination Thermostat (HTT) is open.
Component Heat Termination Thermostat (HTT)
Troubleshooting Check for 24 volts at test point TP10. If no voltage at TP10 after unit has reached
setpoint, HTT is open.
Corrective Action Replace HTT if defective. See Sensor Replacement Section 7.29.
AL60 Defrost Temperature Sensor (DTS)
Cause: Failure of the Defrost Temperature Sensor (DTS) to open.
Component Defrost Temperature Sensor (DTS)
Troubleshooting Test the DTS; see Sensor Checkout Procedure Section 7.29.2.
Corrective Action Replace the DTS if defective. See Sensor Replacement Section 7.29.
AL61 Heater Current Draw Fault
Cause: Improper current draw during heat or defrost mode.
Component Heater(s)
Troubleshooting While in heat or defrost mode, check for proper current draw at heater contactors.
See Electrical Data Section 3.3.
Table 4–5 Alarm Indications and Descriptions
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