7–35
T-372
7.28.2
Sensor Checkout Procedure
This procedures is to be performed to verify the accuracy of a temperature sensor. This procedure describes how
to check using a ice-water bath and also by using an OHM check.
1. Remove the sensor and place in a 0°C (32°F) ice-water bath. The ice-water bath is prepared by filling an
insulated container (of sufficient size to completely immerse the bulb) with ice cubes or chipped ice, then
filling the voids between the ice with water and agitating until the mixture reaches 0°C (32°F) measured on a
laboratory thermometer.
2. Start the unit and check the sensor reading on the control panel. Readings should be 0°C (32°F).
If the reading is correct, reinstall the sensor. If the reading is incorrect, continue with the next step.
3. If the reading is off slightly, then re-calibrate. If the reading is not within 0°C (32°F) +/- 0.25 degrees, replace
the sensor and re-check.
4. A sensor can be tested against from the control box utilizing the carrier harness adapter.
The carrier harness adapter part numbers are 22-50485-00 (CA connector), 22-50486-00 (CC
connector) and 22-50487-00 (ME connector). All readings from the adapter will be resistance readings
with power removed and the harness disconnected from the ML5 controller.
5. Locate the proper wires to be ohmed on the system schematic and check against the temperature
. If unable to soak in an ice bath, the sensor resistance
can be compared against a calibrated sensor located with the sensor being tested.
NOTE
Performing resistance checks on the controller connector is discouraged due to potential damage to the pins.
Resistive Sensors:
• STS, SRS, RTS, RRS: ice-bath, GDP calibration, replace. Remove check against chart. Ambient - easy to
ice-bath check on display, if bad reading replace, remove ohm against chart.
• DTS: ice-bath check on display, if bad replace, can remove and check against chart.
• CPDS: remove from compressor, ice-bath check against display, if bad replace, can remove and check
against chart.
• ETS1 / ETS2: ice-bath check against display, if bad replace, can remove and check against
• USDA 1-4: ice-bath, GDP, remove at socket check resistance