Scotsman MDT5N40A-1B Manual page 24

Scotsman MTD3, MDT4, MDT5, MDT6
Service Diagnostic - Touch Free and Control System
The MDT controller operates the refrigeration and dispensing systems. The on/off of the ice making
system is determined by infrared sensors. Ice or water dispensing is also determined by infrared
sensors. Additionally there is a safety sensor, the water level sensor, that prevents operation if there
isn't any water in the reservoir.
1. Confirm line voltage is being supplied to terminals 1 and 15.
2. No ice, No Water light is On, water in reservoir. This is typically caused by a dirty tip on the water
level sensor. If the tip is clean and undamaged, check for voltage at the Water Sensor pins, it
should read about 12 volts DC. If no voltage, replace the controller. If there is voltage, replace
the sensor. Another check is sensor resistance, the sensor normally reads about 850 ohms at 72
degrees F., higher if colder and lower if warmer. There is no bypass method or part that will allow
operation, only a good sensor will work.
3. Ice is not dispensed when a container is in front of the sensor. First try a non-clear container,
as the sensors infrared light can be absorbed by clear glass. Second, unplug the sensors at the
Dispense connection and jump the two outside pins. The ice dispense relay should engage and
supply power to the dispense motor. If it does not, replace the controller. If it does, replace the
sensors.
Jump outside pins to
test ice dispense relay
Line Voltage
12 volts DC
291-8