Carrier 69NT40-561-300, Operation And Service Manual

Page: 78 / 174

T-365 4–44
AL19 DISCHARGE TEMPERATURE HIGH
Cause: Discharge temperature exceeds 135°C (275°F) for 10 minutes within the last hour.
Component 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.
Component 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
Table 7–
4 .
Corrective Action Correct as required, refer to Refrigerant Charge Table 7.7.1 .
Component 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
Section 7.8 .
AL20 CONTROL CONTACTOR FUSE (F3)
Cause: Control power fuse (F3A or F3B) is open.
Component 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.
Component 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.
Component Check Voltage at QC1:
Troubleshooting If voltage is present, it indicates a defective microprocessor.
Corrective Action Refer to Controller Service Section 7.24 .