Sensor Testing
Water Sensor
The water sensor has two functions, the first is to
stop the machine from operating if there is no
water, the second is to sense the conductivity of
the water supply. This test is for sensing that there
is water in the sump.
1. Test using the controller’s indicator lights (sump
empty and sump full). Shut the water supply to the
unit off. With power supplied to the unit, push and
hold the Clean button until water is pumped out of
the reservoir. The sump empty light should be On.
If not, check the water level and repeat the drain
cycle if needed. Then add water, when there is
water in the reservoir, the sump empty light go out.
When that occurs, the sensor and its circuit are
good. The sump full light has no function in this
model.
2. Test with an ohmmeter. Disconnect electrical
power. Open the control box cover. Unplug the
connector at J9. Locate water level sensor and
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.
Temperature Sensors
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 temperature
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 temperature 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 32 degrees F., check the resistance of each
sensor. The resistance should be within 1000 ohms
of 32649.
May 2008
Page 35
CU1526, CU2026, CU3030
Service Manual
