Control Board Replacement; Harvest Control - Thermistor; Thermistor Check Procedure; Float Switch - Hoshizaki KMD-850MAH Service Manual

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 1, 4, 3, 2. 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

Adjust the dip switches to the factory default settings. See "II.C.3.a) Default Dip Switch
Settings." S4 dip switch #8 must remain off.
If there is a switch present between relay X3 & X4, move it to the "ALP" position.
D. Harvest Control – Thermistor
A thermistor is used as a harvest control sensor. The therminstor's resistance varies
depending on the suction line temperatures. The control board monitors the resistance to
start the harvest timer. No adjustment is required.

1. Thermistor Check Procedure

If necessary, check the resistance between thermistor leads, and visually check the
thermistor mounting, located on the suction line next to the evaporator outlet. To check
the resistance between thermistor leads, follow the steps below.
1) Disconnect the connector K3 on the board.
2) Remove the thermistor. See "V.I. Removal and Replacement of Thermistor."
3) Immerse the thermistor sensor portion in a glass containing ice and water for 2 or
3 minutes.
4) Check the resistance between thermistor leads. Normal reading is within 4.7 to 6.2 kΩ.
Replace the thermistor if it is outside the normal reading.
E. Float Switch
The float switch is used to determine that there is sufficient water in the tank after the
1 minute fill cycle and after each harvest cycle. The float switch is also used to determine
that the appropriate volume of water has been converted into ice before switching out of
the freeze cycle. No adjustment is required.

1. Float Switch Check Procedure

To check the float switch, follow the steps below.
1) Turn off the power supply.
2) Remove the front panel and move the control switch to the "OFF" position.
3) Remove the insulation panel. Remove cube guide B, then remove cube guide A.
Remove the overflow cap, overflow pipe, and water shield. See Fig. 1.
4) Remove the drain plug and drain the water tank. Replace the drain plug in its correct
position. Be careful not to cross thread it.
5) Replace the water shield, overflow pipe, overflow cap, cube guide A, and cube guide B
in their correct positions. Be careful not to cross thread the overflow pipe.
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