Temperature Sensors; Test Procedures - Loads - Scotsman MVP456 Service Manual

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remove it from the sump cover. Test 1: Place one
lead of the ohmmeter on the longest probe and
the other on the controller end of the red wire,
there should be continuity. Test 2: Place one lead
on the controller end of the white wire and the
other on the mid-length probe, there should be
continuity. Test 3: Place on lead on the controller
end of the black wire and the other on the
shortest probe, there should be continuity.
If not, clean the probes and recheck.
3. Test the controller's water level sensor circuit.
Reconnect electrical power. Unplug harness from
water level sensor, the sump empty light should
be ON. Jump harness wires white and black. The
sump full light should be ON. Jump harness
wires black and red, the sump full and sump
empty lights will be OFF. Check harness wire by
wire for continuity if there is no reaction from the
controller during this test.
TEMPERATURE SENSOR
1. Check controller. If the sensor calibration is
completely out of range, the code display will
read either 5 or 7.
2. Check with an ohmmeter. Open control box
cover, unplug sensor from J6. Water temperatu-
re probe: Measure the temperature of the water.
Push and release the clean button. Wait one
minute. Measure the resistance of the water
probe (two leads next to the open socket) and
compare to the resistance in the chart for that
temperature. Any reading within 1000 ohms is
acceptable. Discharge sensor: Measure the tem-
perature of the discharge line as close to the
sensor as possible. Measure the resistance of
the discharge temperature sensor (two leads
farthest away from the open socket on the harness
connector) and compare to the resistance in the
chart for that temperature. Any reading within
1000 ohms is acceptable.
3. Alternate procedure: Remove both water
and discharge sensors from their places on the
ice machine. Put both into a container of ice
water. Put a thermometer in the water. When the
thermometer is at 0°C (32 degrees F), check the
resistance of each sensor. The resistance should
be 32650 ohms
°C
0
10
15
20
25
30
35
WATER
TEMP.
SET
Compressor
Failure to start.
Single phase models. All have resistance start,
capacitor run type motors. Check voltage to
compressor at the contactor. Compare the idle
voltage (compressor off) to the active voltage
(compressor starting). The supply voltage must
not be less than the lowest rated voltage for the
ice machine. If the voltage is correct, proceed to
the next step.
Page 25
Ohms
32650
19000
15715
12495
10000
8055
6530
DISCHARGE
TEMP.
SET