Service Diagnosis - Scotsman NDE754 Service Manual

SERVICE DIAGNOSIS

Symptom
No ice is made, nothing operates
No ice, auger motor is turning
Unit makes ice, but very slowly.
Possible Cause
Unit off due to no power
Unit off due to master switch in
OFF position.
Unit off due to low water level.
Unit off due to ice level sensors
(photo-electric eyes) blocked.
Unit off due to scale on water level
sensor.
Unit off due to high pressure
control open.
Auger motor hums but does not
turn.
Unit is shut down
Low pressure control open
No power to circuit board.
Circuit Board gear motor relay will
not close
Water level or ice level sensor
failed.
Compressor contactor coil is open Check/replace contactor
Compressor will not start
Circuit board compressor relay will
not close.
High discharge pressure because
of a dirty condenser
Low capacity because the auger
and evaporator are coated with
mineral scale
Low suction pressure due to low
refrigerant charge
March 2000
Page 19
NDE754
Probable Correction
Restore Power
Switch master switch to ON.
Check water supply, filter, strainer,
float valve. Correct water supply.
Check/clean ice level sensors.
Clean water level sensor.
Check for water interruption (water
cooled) or fan motor failure (air
cooled).
Auger can't turn. Circuit board has
not yet shut unit down.
Circuit board has shut ice machine
down due to high auger motor amp
draw. Check for cause of high amp
draw, including bearings,
gearmotor condition and scale on
auger and in evaporator.
Auger not turning due to: motor
failure; auger relay failure on circuit
board; or gears stripped. Check
drive train.
TXV restricted or not metering.
Check bulb temperature.
Lack of refrigerant. Check for leak.
Check for a restricted system
Check harness
HI or low pressure cut out open
Check, replace board
Check, replace sensor
Check start capacitor.
Check start relay
Check compressor windings
Check, replace board
Clean the air filter and condenser.
Clean the water system
Locate leak. Recover refrigerant,
repair leak, replace dryer,
evacuate and weigh in the
nameplate charge