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LCD Touchscreen & Microprocessor
Control Board
FUNCTION
Touch screen is the user interface with the machine and
sends input to the control board.
Microprocessor Control Board (MCB) monitors inputs
and sends signals to the IO board to energize and de-
energize components.
SPECIFICATIONS
The LCD touchscreen display and microprocessor
control board are contained in one module.
CHECK PROCEDURE
1. Reboot machine by moving toggle switch off/on
Refer to appropriate fl owchart for the problem you
are encountering. Touch screen and microprocessor
control board diagnostics are covered by a process of
elimination. Use the individual fl ow charts unless the
LCD screen is entirely black (no power) or entirely white
(powered).
Touch screen is black
• Verify processor board has energized lights - Refer
to Will not Run fl owchart for no lights.
• Verify touchscreen power connector is connected to
control board.
Touch screen is white
• Verify strip connector is secure and connected by
removing and reinserting connector.
• Lift lock
• Remove and evenly reinsert strip into connector.
• Depress lock to secure strip.
• Inspect strip to verify even placement.
• Replace touchscreen and control board assembly.
Cabinet Temperature Thermistor
FUNCTION
Supplies input to control board to indicate cabinet
temperature. The control board energizes and de-
energizes the compressor based on input from this
thermistor.
SPECIFICATIONS
10,000 Ohms ± 2% at 25°C (77°F)
CHECK PROCEDURE
NOTE: Use a multimeter to check operation.
1. Reboot machine by moving toggle switch off/on.
2. Inspect for correct wiring.
3. Isolate by disconnecting the wiring connectors.
4. Check continuity across the terminals with an ohm
meter.
• Resistance = Thermistor is good
• Open (OL) = Replace thermistor
NOTE: This thermistor is identical to the the duct
temperature thermistor. Swapping the two thermistor
connections at the IO board can be used for
diagnostics.
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