Washer Fluid Level Switch: Description and Operation

Fig.20 Washer Fluid Level Switch (Viewed From Bottom Of Reservoir):

The washer fluid level switch is a single pole, single throw reed-type switch mounted near the front of the washer reservoir, forward of the two washer pump/motors. Only the molded plastic switch mounting flange and connector receptacle are visible when the switch is installed in the reservoir.

A short nipple formation extends from the inner surface of the switch mounting flange, and a barb on the nipple near the switch mounting flange is press-fit into a rubber grommet seal installed in the mounting hole of the reservoir. A small plastic float pivots on the end of a bracket that extends from the switch nipple formation. Within the float is a small magnet, which actuates the reed switch. The washer fluid level switch cannot be adjusted or repaired. If faulty or damaged, the switch must be replaced.

The washer fluid level switch uses a pivoting, oblong float to monitor the level of the washer fluid in the washer reservoir. The float contains a small magnet. When the float pivots, the changing proximity of its magnetic field will cause the contacts of the small, stationary reed switch to open or close. When the fluid level in the washer reservoir is at or above the float level, the float moves to a vertical position and the switch contacts open. When the fluid level in the washer reservoir falls below the pivoting float, the float moves to a horizontal position and the switch contacts close. The switch is connected to the vehicle electrical system through a dedicated take out and connector of the left headlamp and dash wire harness. The switch receives a five volt reference signal from the Body Control Module (BCM) through the washer fluid switch output circuit. The switch is grounded at all times through another take out of the left headlamp and dash wire harness with a single eyelet terminal connector that is secured under a ground screw near the top of the left front fender inner shield in the engine compartment.

When the switch closes, the BCM senses the voltage change on the circuit. The BCM is programmed to send low washer fluid messages to the Electronic Vehicle Information Center (EVIC) over the Programmable Communications Interface (PCI) data bus. The EVIC is programmed to respond to this message by displaying the Washer Fluid Low warning and sending a chime request message back to the BCM over the PCI data bus. Then the BCM generates an audible chime tone warning. A resistor within the washer fluid level switch allows the BCM to monitor and diagnose this circuit. The BCM will store a Diagnostic Trouble Code (DTC) for any fault that it detects. For retrieval of this fault information and further diagnosis of the washer fluid level switch, the BCM, the EVIC, the PCI data bus, the BCM message outputs to the EVIC that control the Low Washer Fluid indicator, or the EVIC message outputs to the BCM that control chime service, a DRB III scan tool and the appropriate diagnostic information are required.