Control Board Replacement; Harvest Control - Thermistor; Thermistor Check Procedure; Float Switch - Hoshizaki KM1601SRH350 Service Manual

5. Control Board Replacement

Before replacing a control board that does not show a visible defect and that you suspect
is bad, see "II.C.4. Control Board Check Procedure." Before installing the new control
board, adjust the S4 dip switches to the factory default settings. See "II.C.3.a) Default
Dip Switch Settings." S4 dip switch 8 must remain off. The "C" "ALP" switch should be in
the "ALP" position.
D. Harvest Control – Thermistor
A thermistor is used as a harvest control sensor. The thermistor's resistance varies
depending on suction line temperature. 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 thermistor connector from the K3 connector on the control board.
) Remove the thermistor. See "V.L. Removal and Replacement of Thermistor."
3) Immerse the thermistor sensor portion in a glass containing ice and water for  or
3 minutes.
4) Check the resistance between thermistor leads. Normal reading is within 4.7 to 6. 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.
) Remove the front panel and move the control switch to the "OFF" position.
3) Remove the insulation panel, then remove the cap located on the front bottom part of
the ice dropping hole. Drain the water tank.
4) Replace the cap in its correct position. Be careful not to cross thread it.
5) Remove the control box cover.
6) Disconnect the black float switch connector from the K5 connector on the control board.
7) Check for continuity across the float switch leads. With the water tank empty, the float
switch should be open. If open, continue to step 8. If closed, follow the steps in "II.
E.. Float Switch Cleaning." After cleaning the float switch, check it again. Replace if
necessary.
8) Reconnect the black float switch connector, then replace the control box cover in its
correct position.
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