Liquid Level Sensor Checkout
RTHC-SVD01B-EN 51
Section 9 Liquid Level Sensor Checkout
9-1. General
The sensor consists of a body made from an enclosed tube, fitting, and
a magnetic float which slides over the tube. The liquid level sensor is
required to provide input necessary for the control of the Electronic
Expansion Valve(EXV).
The Stepper module monitors the Liquid Level Sensor (LLS) under
normal operating conditions and modulates the EXV in accordance
with the level of refrigerant in the evaporator. If the liquid level rises
above the optimum value of 0.0” as displayed in the Refrigerant Report
Menu, the EXV will begin to close. If the liquid level falls below the opti-
mum value of 0.0” as displayed on UCP2, the EXV will begin to open.
A malfunctioning Liquid Level Sensor can exhibit several different
diagnostics. A diagnostic will appear if the LLS is failing electrically or if
the stepper module is defective. Use the following procedure to deter-
mine the cause of the diagnostic.
9-2. Checkout procedure
Use a Voltmeter set to DC Volts:
4. Measure the voltage from terminal J7-1 to J7-3. You should mea-
sure between 4.75 and 5.25 VDC.
5. If the measurement is between 4.75 and 5.25 volts, skip ahead to
step 6.
6. If the above measurement does not fall between 4.75 and 5.25
VDC, disconnect the sensor from the module and re-measure the
voltage at the module.
7. If the measurement with the sensor disconnected is still out of
range, the module is defective and should be replaced.
8. If the measurement with the sensor disconnected is in range, the
sensor is defective and should be replaced.
9. Measure the voltage from J7-2 to J7-3 on the RTHC Stepper
module with the sensor connected.
10. The voltage should measure between 0.5 and 4.5 VDC. If it is not,
replace the sensor.
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