Controller Differences - Scotsman MVP456 Service Manual

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will be ON. If the water valve does not open to fill
the reservoir when its indicator light is on, do a
voltage check. Shut the unit down by holding the
Off button in for 3 seconds. Unplug the harness
connection from the inlet water valve. Wait four
minutes. Push and release the On button to
restart the machine. After the unit drains the
reservoir, the inlet water valve connection should
receive full voltage. If it does, the inlet water valve
should be replaced. If there is no voltage, check
voltage from the controller to ground. The inlet
water solenoid valve pin is 7. If there is voltage
from that pin to ground, but low voltage at the
valve harness connection, the harness has a
broken wire or poor connection and must be
replaced. If the voltage to ground is low, the
controller should be replaced.
2. Test using an ohmmeter. Disconnect
electrical power. Unplug coil from harness.
Measure coil resistance. If open, replace the inlet
water solenoid.
Harvest assist solenoid
1. Test using the controller's indicator lights.
Push and release the Harvest button. The Hot
Gas indicator light will be on. At the same time the
Harvest Assist Solenoid will be powered. If the
ice on the evaporator is thin, the solenoid will
extend. If the ice is nearly full sized, the solenoid
will press against the ice until it releases from the
evaporator, then the solenoid probe will extend.
If the probe extends, the solenoid is good. If not,
do a voltage check. Unplug the high voltage
harness from the harvest assist solenoid. Attach
a voltmeter to the harness connector. Push and
release the Harvest button. There should be full
voltage at the connector.
If there is and the solenoid does not extend,
replace the solenoid. If full voltage is not present,
check voltage at the controller. If there is no
voltage, check voltage from the controller to
ground. The hot gas / harvest assist pin is 5. If
there is voltage from that pin to ground, but low
voltage at the solenoid harness connection, the
harness has a broken wire or poor connection
and must be replaced. If the voltage to ground is
low, the controller should be replaced.
Note: The coil of this valve is internally rectified,
will normally show infinite resistance when
tested with an ohmmeter.
Hot Gas Valve
1. Test using the controller's indicator lights. If
the unit is running, or has been off for more than
4 minutes, push and release the Harvest button.
The Hot Gas indicator light will be on and the hot
gas valve will be energized. The compressor will
force discharge gas into the evaporator inlet,
warming it. If the evaporator inlet does not warm
up, do a voltage check. Shut the unit off by
holding the Off button in for 3 seconds. Unplug
the high voltage harness from the hot gas
solenoid. Attach a voltmeter to the harness
connector. Wait 4 minutes. Push and release the
Harvest button. There should be full voltage at
the connector. If there is and the solenoid does
not open, replace the solenoid coil. If full voltage
is not present, check voltage at the controller. If
there is no voltage, check voltage from the
controller to ground. The hot gas pin is 5. If there
is voltage from that pin to ground, but low voltage
at the solenoid harness connection, the harness
has a broken wire or poor connection and must
be replaced. If the voltage to ground is low, the
controller should be replaced.
2. Test with an ohmmeter. Disconnect electrical
power. Unplug high voltage harness from hot gas
or vapor valve. Measure resistance of hot gas or
vapor valve coil. If open, replace the coil.

CONTROLLER DIFFERENCES

The controllers are programmed at the factory for
the model they are installed on, they cannot be
moved from one model to another due to
differences in:
• Water purge time per setting
• Maximum harvest time
• Number of evaporator plates
The service controller has a selector switch that
allows it to be used as a replacement part in any
of the Prodigy models in production at the time
the controller was manufactured. As new Prodigy
models are introduced, those models will be
added to the list of models new service controllers
will work with.
The Service Controller includes a selector switch.
The switch must be set to the model the controller
is being installed on. As new models are
introduced, their setting will be added to service
controllers produced after that point.
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