Carrier PrimeLINE 69NT40-561-200 Operation And Service Manual page 79

AL19 DISCHARGE TEMPERATURE HIGH
Component
Corrective Action Correct as required. Refer to Refrigerant Charge
Component
Corrective Action If the alarm persists, it may indicate a failing compressor, replace the
AL20 CONTROL CONTACTOR FUSE (F3)
Cause: Control power fuse (F3A or F3B) is open.
Component
Corrective Action If short is found, replace the defective coil.
Component
Corrective Action Replace the defective coil.
Component
Corrective Action Refer to Controller Service
AL21 CONTROL CIRCUIT FUSE (F1/F2)
Cause: One of the 18 VAC controller fuses (F1 / F2) is open. Refer to Cd08.
Component
Corrective Action Replace defective sensor(s).
Component
Corrective Action Repair as needed.
Component
Corrective Action Replace controller. Refer to Controller Service
Non-condensables in the refrigeration system.
Troubleshooting With the unit off allow system to stabilize to ambient temperature.
Check system pressure against Pressure Temperature Chart. Refer
to Table
Additional Alarms such as AL16, AL24.
Troubleshooting Check compressor operation.
compressor. Refer to Compressor Service
Check F3A fuse.
Troubleshooting If fuse is open, check PA, PB, CH coils for short to ground.
Replace the fuse.
Check F3B fuse.
Troubleshooting If fuse is open, check ESV coil resistance at TP7 to TP9. If short to
ground, or if resistance 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.
Replace the fuse.
Check Voltage at QC1.
Troubleshooting If voltage is present, it indicates a defective microprocessor.
System Sensors
Troubleshooting Check system sensors for short to ground.
Wiring
Troubleshooting Check wiring for short to ground.
Controller
Troubleshooting Controller may have an internal short.
7–4, Table 7–5.
Section
4–41
Section 7.7.1.
Section 7.9.
7.27.
Section 7.27.
T-362