Control Board Check Procedure - Hoshizaki KM-251BAH Service Manual

Self-contained crescent cuber

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wire is common) and two separate switches. Check the upper switch by ohming out the

black and red wires. When the ﬂoat is up, the switch should be closed. Check the lower

switch by ohming out the black and blue wires in the same manner. If either switch fails,

the assembly should be replaced.

6. Control Board Check Procedure

Before replacing a control board 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.

1) Check the S4 dip switch settings to assure that they are in the factory default positions.

2) Turn the control switch to ICE and check for proper control voltage. If the red LED is on,

the control voltage is good. If the red LED is off, check the control transformer circuit.

3) Check the 115 volt input at the 10-pin connector. Check the brown and white wire at

pin #10 to a white neutral wire for 115 volts. (Always choose a white neutral wire to

establish a good neutral connection when checking voltages.) A jumper also feeds 115

volts into pin #7. If no voltage is present, check the 115 volt supply circuit.

4) The output test switch provides a relay sequence test. Make sure the control switch is in

the ICE position, then press the output test switch. The correct lighting sequence should

be none, 2, 3, 4, 1, and 4, normal sequence every 5 seconds. Components (e.g., the

compressor) will cycle during the test. Note that the order of the relays from the outer

edge of the board is 1, 4, 3, 2.

Note: If the LEDs light in a different sequence or the 5–second interval does not occur,

the control board is bad and should be replaced.

5) After checking the sequence, the unit automatically resumes normal operation after the

test. The unit begins normal operation with the 1 minute ﬁll cycle.

Red (upper)

Black (common)

Blue (lower)

Magnet (towards top)

Upper Float (blue)

Spring Retainer Clip

Magnet (towards top)

Lower Float (white)

Plastic Retainer Clip

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