Carrier 69NT40-561-399 Operation And Service Manual page 78

AL19 DISCHARGE TEMPERATURE HIGH
Cause: Discharge temperature exceeds 135°C (275°F) for 10 minutes within the last hour.
Component
Component
Component
AL20 CONTROL CONTACTOR FUSE (F3)
Cause: Control power fuse (F3A or F3B) is open.
Component
Component
Component
T-365
Restrictions in the refrigeration system.
Troubleshooting Ensure the Discharge Service Valve is fully open.
Corrective Action Open the Discharge Service Valve as needed.
Troubleshooting Check the unit for air flow restrictions.
Corrective Action Clean or remove any debris from coils.
Non-condensables in the refrigeration system.
Troubleshooting With the unit off allow system to stabilize to ambient temperature.
Check system pressure against PT Chart for 134a, refer to
4.
Corrective Action Correct as required, refer to Refrigerant Charge
Additional Alarms such as AL16, AL24.
Troubleshooting Check compressor operation.
Corrective Action If the alarm persists, it may indicate a failing compressor, replace the
compressor, refer to COMPRESSOR Service
Check F3A, if the fuse is open:
Troubleshooting Check PA, PB, CH coils for short to ground, if short is found:
Corrective Action Replace the defective coil.
Replace the fuse.
Check F3B, if the fuse is open:
Troubleshooting Check ESV coil resistance at TP7 to TP9, if short to ground, or if re-
sistance is less than 4 ohms, coil is defective.
Check CF, ES, EF, HR coils for short to ground, if short is found, coil
is defective.
Corrective Action Replace the defective coil.
Replace the fuse.
Check Voltage at QC1:
Troubleshooting If voltage is present, it indicates a defective microprocessor.
Corrective Action Refer to Controller Service Section
4–44
Table 7–
Table 7.7.1.
Section 7.8.
7.24.