Scotsman MDT2 - Manual (Page 19)

SERVICE DIAGNOSIS
SYMPTOM POSSIBLE CAUSE SUGGESTED CORRECTION
Unit will not run Blown fuse in P.C. Board Replace fuse & check for cause of blown
fuse
No LED lights Master switch in OFF position Turn switch to ON position
Inoperative P.C. Board Replace P.C. Board
Loose electrical connections Check wiring
6th Yellow LED glows Inoperative or dirty ice level control Replace or clean ice level control
5th Yellow LED glows Shortage or too soft water See remedies for shortage of water or
install a mineral salt metering device
2nd LED glows High head pressure Dirty condenser. Clean
Inoperative fan motor. Replace
3rd Yellow LED blinks Too high evap. temperature Check and charge refrigerant system
Shortage or lack of refrigerant
3rd Yellow LED glows Gear motor tends to run on reverse Check gear motor capacitor
Too low gear motor rotating speed Check rotor bearings, freezer bearings and
interior of freezer for scores. Replace
whatever is worn or damaged.
No rotation of gear motor Check for power to drive motor (16 A
fuses)
Check for stator winding
Gear motor starts and stops Check for correct operation of drive after a
while motor magnetic sensor
Check for correct magnetic capacity of
magnetic cylinder
Compressor cycles intermittently Low voltage Check circuit for overloading
Check voltage at the supply to the
building. If low, contact the power
company
Non-condensable gas in system Purge the system
Compressor starting device with loose
wires Check for loose wires in starting device
Low ice production Capillary tube partially restricted Blow charge, add new gas & drier, after
evacuating system with vacuum pump
Moisture in the system Same as above
Low water level in the freezer Adjust to approx 20mm below ice spout
Shortage of refrigerant Check for leaks & recharge
Pitted or stained auger surface Clean or replace auger
Will not dispense Dispense motor open Check windings
No power to dispense motor Check harness connections from
touch free sensors to control board &
from board to motor
Control board does not work Trace harness from touch free
sensors to PC board, jump the two
center pins, the dispense motor
should turn. If not replace the board
Open harness Check the harness for continuity, if
any wire is open, replace the harness
Defective sensor If the above does not prove to be a
problem, replace the sensors
MDT2
May 2002
Page 19