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B. Control Board Check
Before replacing a CB that does not show a visible defect and that you suspect is bad,
always conduct the following check procedure. This procedure will help you verify your
diagnosis. Always choose a neutral (W wire) to establish a good neutral connection
when checking high voltages.
Alarm Reset: If CB is in alarm (beeping), press the "ALARM RESET" button on CB
with power on. For alarm information, see "II.E.3. LED Lights and Alarm
Safeties Chart."
1) Check S3 dip switch settings to assure that they are in the factory default position. For
factory default settings, see "II.E.4.Default Dip Switch Settings."
2) Move the power switch to the "ON" position. If the "POWER OK" LED is on, CB control
voltage (10VAC) is good. If the "POWER OK" LED is off, check CT circuit. CT output is
10VAC at 115VAC primary input. If the secondary circuit has proper voltage (10VAC)
and the "POWER OK" LED is off, CB is bad and must be replaced.
If the secondary circuit does not have proper voltage, check CT primary circuit and
incoming voltage to a neutral (W wire).
3)
The "OUTPUT TEST" button provides a relay sequence test. Move the power switch to
the "ON" position. Next, press the "OUTPUT TEST" button. CB cycles through all relays
in sequence. The correct LED lighting sequence is 3, 2, 1, 4, 5. Note that the order of
the LEDs from the outer edge of the board is 5, 4, 1, 2, 3. Components (e.g., Comp)
cycle during the test. Following the output test, the appliance resumes operation. If the
LEDs do not light as described above, CB is bad and must be replaced.
4) Confirm Clogged Filter Thermostat: Check for 5VDC at CB K6 connector pin #2 (P wire)
to K5 connector pin #2 (open). If 5VDC is not present, CB is bad and must be replaced.
5) Door Switch: Check for 5VDC at CB K6 connector pin #4 (LBU wire) to K5 connector pin
#2 (open). If 5VDC is not present, CB is bad and must be replaced.
6) High-Pressure Switch: Check for 5VDC at CB K6 connector pin #6 (V wire) to
K5 connector pin #2 (open). If 5VDC is not present, CB is bad and must be replaced.
7) Confirm proper output voltage (3.8VDC) at RED K4 connector (CTh) pin #1 to pin
#2 gray (GY) wires and WHITE K3 connector (DTh) pin #1 to pin #2 orange (O) wires. If
no voltage is present, CB is bad and must be replaced.
8) As the appliance cycles through the sequence of operation, check for 115VAC from
K1 and K9 connector pins to a neutral (W wire).
Relay LED
Component Energized
LED
ON/OFF
Control Board
Connector
X1
1
Defrost Heater (Freezer)
ON
K1 Pin #6
X2
2
Cabinet Light (door switch)
ON
K1 Pin #5
X3
3
Evaporator Fan Motor
OFF
K1 Pin #3
X4
4
Compressor Relay
ON
K1 Pin #10
X5
5
Condenser Fan Motor
Condensate Pan Heater (RFH1)
ON
K9 Pin #2
Legend:
CB
–control board;
Comp
–compressor;
CT
–control transformer;
CTh
–cabinet
thermistor;
DH
–defrost heater;
DTh
–defrost thermistor