Control Board Check Procedure; Control Board Replacement - Hoshizaki KM-515MAH Service Manual

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 S4 dip switch settings to assure that #3, 4, 7, 8, 9, & 10 are in the factory
default position. Switches 1, 2, 5, & 6 are cleaning adjustments and the settings are
flexible.
2) Move the control switch to the "ICE" position. The red "POWER OK" LED should come
on. If the LED is off, check the control transformer secondary circuit. The transformer
secondary circuit includes the cleaning valve interlock switch. Make sure the interlock
switch is closed; otherwise, no control voltage is supplied to the K2 connector.
Transformer output is 10.5V at 115V primary input. If the secondary circuit has proper
voltage and the red LED is off, the control board is bad and should be replaced.
If the secondary circuit does not have proper voltage, check the control transformer
primary circuit. Check for 115V at the 10-pin connector. Check the brown wire at pin
#10 to a white neutral wire for 115V. (Always choose a white neutral wire to establish a
good neutral connection when checking voltages.) For additional checks, see "IV.B.1.[1]
The icemaker will not start."
3) The "OUTPUT TEST" button provides a relay sequence test. Make sure the control
switch is in the "ICE" position, then press the "OUTPUT TEST" button. The correct
lighting sequence should be none, 2, 3, 4, 1. Some 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. After checking the sequence, the unit automatically starts at the
1 minute fill cycle. If the LEDs light in a different sequence, the control board is bad and
should be replaced.

5. Control Board Replacement

The application switch located between relay X3 & X4 must be set to the "ALP" position.
The dip switches should be adjusted to the factory default settings. See "II.C.3.a) Default
Dip Switch Settings." S4 dip switch #8 must remain off.
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