Hoshizaki KM-650MRH, KM-650MAH, KM-650MWH Control Board Check Procedure, Control Board Replacement

4. 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 dip switch settings to assure that #3, 4, 7, 8, 9, & 10 are in the factory default position. On units with a slide-type output test switch, the output test switch (S3) should be OFF. Switches 1, 2, 5, & 6 are cleaning adjustments and the settings are flexible.

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 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. On units with a slide-type output test switch, move the control switch to the OFF position, move the output test switch to the ON position, then move the control switch to the ICE position. On units with a push- type output test switch, 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, place the output test switch back in the OFF position

on units with a slide-type switch. The output test switch must remain in the OFF position during normal operation. On units with a push-type output test switch, the unit automatically resumes normal operation after the test. The unit begins normal operation with the 1 minute fill cycle.

5. Control Board Replacement

The application switch located between relay X3 & X4 must be set to match the original board application. Place this switch in the ALP position if there is no white wire supplied to the K1 connector. If there is a white wire, place the switch in the C position. If this switch is placed in the wrong position either the compressor contactor will remain energized with the control switch OFF or the unit will not start.

The dip switches should be adjusted to the factory default settings as outlined in this manual. Dip switch #8 must remain in the OFF position.

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