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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.
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
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.F. 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
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 base cover. Remove the pump tubing from the tank. See Fig. 1. Allow the
water to drain from the tank. Replace the pump tubing and base cover in their correct
positions.
4) Remove the control box cover.
5) Disconnect the black float switch connector from the K5 connector on the control board.
6) Check for continuity across the float switch leads. With the water tank empty, the float
switch should be open. If open, continue to step 7. If closed, follow the steps in "II.
E.2. Float Switch Cleaning." After cleaning the float switch, check it again. Replace if
necessary.
7) Reconnect the black float switch connector, then replace the control box cover.
8) Move the control switch to the "ICE" position. Replace the front panel, then turn the
power supply on. After 1 minute, the 1 minute fill cycle should end and the initial
harvest cycle should begin. If the initial harvest cycle begins, the float switch is good
and the check is complete. If the initial harvest cycle does not begin, continue to step 9.
