Washer Fluid Level Switch - Operation

OPERATION

The washer fluid level switch uses fluid conductivity to monitor the level of the washer fluid in the washer reservoir. Electricity is conducted between the two switch pins or electrodes only when they are immersed in the washer fluid, which closes the switch circuit. When the fluid level in the washer reservoir falls below the pins, electrical current cannot be conducted and the switch becomes an open circuit, which signals a low fluid condition.

In order to prevent an electrical charge from accumulating in the electrical leads of the switch, the switch receives current that is pulsed from the Body Control Module (BCM) (also known as the Common Body Controller/CBC) located in the passenger compartment. The BCM monitors the switch return signal and is programmed to respond to three consecutive open switch readings by sending an electronic washer fluid indicator lamp-ON request message to the Instrument Cluster (IC) (also known as the Common Instrument Cluster/CIC) over the Controller Area Network (CAN) data bus. The IC responds to this message by illuminating the washer fluid indicator and by sounding an audible chime tone warning.

The washer fluid level switch is connected to the vehicle electrical system through a dedicated take out and connector of the headlamp and dash wire harness. The switch is connected in series between a sensor return circuit and the washer fluid switch sense input to the BCM.

The washer fluid level switch and the hard wired circuits between the switch and the BCM may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the washer fluid level indicator or the electronic controls or communication between other modules and devices that provide some features of the washer system. The most reliable, efficient, and accurate means to diagnose the washer fluid level indicator or the electronic controls and communication related to washer fluid level switch operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.