T-372
4–38
AL020
Control Fuse (F3) Open
Cause:
Control power fuse (F3 or F4) is open.
Component
Check F3 fuse.
Troubleshooting
If fuse is open, check PA, PB, CH coils for short to ground.
Corrective Action
If short is found, replace the defective coil. Replace the fuse.
Component
Check F4 fuse.
Troubleshooting
If fuse is open, check ESV coil resistance at CA1 to TRX2. 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.
Corrective Action
Replace the defective coil. Replace the fuse.
Component
Check voltage at QC1.
Troubleshooting
If voltage not present, check ST7. If voltage is present, it indicates a
defective microprocessor.
Corrective Action
See Controller Service
.
AL021
Control Fuse (F1 / F2) Open
Cause:
One of the 18 VAC controller fuses (F1 or F2) is open. Refer to Cd08.
Component
System Sensors
Troubleshooting
Check system sensors for short to ground.
Corrective Action
Replace defective sensor(s).
Component
Wiring
Troubleshooting
Check wiring for short to ground.
Corrective Action
Repair as needed.
Component
Controller
Troubleshooting
Controller may have an internal short.
Corrective Action
Replace controller. See Controller Service
.
AL022
Evaporator IP Open
Cause:
Evaporator motor internal protector (IP) is open.
Component
Evaporator Motor
Troubleshooting
Shut down unit, disconnect power. Check harness between CA22 and
CA12. If open circuit, check Evaporator Motor IP at plug connection pins
4 & 6.
Corrective Action
Replace defective Evaporator Fan Motor. See Evaporator Fan Motor
Service
.
AL023
Loss of Phase B
Cause:
Compressor is running and controller determines that compressor internal protector and HPs are
closed. Or, the High Speed Evaporator Fan motor is energized and internal protector is not tripped
and current reading is less than 0.5 amps.
Component
Incoming Power
Troubleshooting
Verify proper voltage input and proper operation of compressor contactor
and high speed evaporator contactor.
Corrective Action
Replace defective component.