Special Detailed Diagnosis; Testing The Power Pcb & Display/Control Pcb; Testing The Condenser Fan; Testing The Evaporator Fan - EdgeStar CWB8420DZ Service Manual

9.4 Special Detailed Diagnosis

9.4.1 Testing the Power PCB & Display/Control PCB
1. The control system including the POWER PCB and DISPLAY/CONTROL PCB operates when
the unit is powered on. If the unit is receiving power and is switched ON but is not operating
check the control system including the power PCB, display/control PCB and connecting
wires.
2. To Check The Main PCB,
Disconnect the unit from the power source.
Remove the electrical box from the compressor compartment and take out the power PCB.
Disconnect the connectors for all fan motors and the compressor.
Carefully situate the PCB so that it is insulated from other parts and from grounding.
Connect the unit to the power source.
Check the output voltage of all fan motors and compressor connectors on the main PCB.
The correct output voltage of all fan motors connectors should be 12V DC. The correct
output voltage of compressor connector should be same as the power source. If not, the
PCB must be replaced.
3. Replace the Display/Control PCB for the following symptoms after you confirm that the
power PCB is normal.
No LED temperature display or indicator illuminated on the control panel.
Some LEDs do not light.
No response when touching the control buttons. For this symptom, check to see if there
any response after disconnecting and reconnecting the power before replacing the
Display/Control PCB.
The unit does not run correctly in the TEST MODE. In order to run in TEST MODE, Touch
and hold the "LIGHT" and "UP" marks at the same time for 5 seconds.
5. If you can't find the failure from these symptoms, replace the Power PCB and
Display/Control PCB separately to see which one is defective and replace it.

9.4.2 Testing the Condenser Fan

1. The condenser fan motor operates in parallel with the compressor. If the compressor runs
but the motor doesn't, the motor is either defective or disconnected. If neither operates,
check the Power PCB and the cabinet wiring.
2. To Check The Condenser Fan Motor:
Disconnect the unit from the power source.
Disconnect the condenser fan motor lead connector from the cable.
Connect the condenser fan to a 12V DC power source. If the motor fails to operate, it is
defective and must be replaced.

9.4.3 Testing the Evaporator Fan

1. The evaporator fan motor operates when the compressor operates and the rest of the time
cycles ON and OFF to circulate the interior air. If the compressor runs but the fan doesn't, the
motor is either defective or disconnected. If neither operates, check the Power PCB and the
cabinet wiring.