Commander 4WD V8-4.7L VIN N (2006)
Washer Fluid Level Switch: Description and Operation
SENSOR-WASHER FLUID LEVEL
DESCRIPTION
The washer fluid level switch is a single pole, single throw reed-type switch mounted on the left outboard side of the washer reservoir (5), just rearward
of the washer pump/motor. Only the molded plastic switch mounting flange (2) and the integral connector receptacle (1) are visible when the switch is
installed in the reservoir. A short nipple formation (3) extends from the inner surface of the switch mounting flange, and a barb on the nipple is pressed
through a rubber grommet seal (6) installed in the mounting hole of the reservoir.
A small, molded plastic float (4) has two pivot pins (7) near its center that are snapped into two receptacles near the ends of two stanchions that extend
toward the float from the nipple formation. A small magnet (8) is secured within the end of the float nearest the nipple, and a reed switch is concealed
within the nipple. A diagnostic resistor is connected between the two switch terminals within the switch mounting flange.
The washer fluid level switch cannot be adjusted or repaired and, if ineffective or damaged, it must be replaced.
OPERATION
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 proximity of this magnet to a stationary reed switch within the nipple formation of the switch changes. When the fluid
level in the washer reservoir is at or above the float level, the float moves to a vertical position, the influence of the float magnetic field is removed from
the reed switch, and the normally open reed switch contacts open. When the fluid level in the washer reservoir falls below the level of the pivoting float,
the float moves to a horizontal position, the influence of the float magnetic field is applied to the reed switch, and the contacts of the normally open reed
switch close.
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 clean ground output of the Front Control Module (FCM) on a sensor return circuit and the washer
fluid switch sense input to the FCM. When the switch closes, the FCM senses the ground on the washer fluid switch sense circuit. The FCM is
programmed to respond to this input by sending an electronic washer fluid indicator lamp-on message to the instrument cluster over the Controller Area
Network (CAN) data bus. The instrument cluster responds to this message by illuminating the washer fluid indicator, sounding an audible chime tone
warning and suppressing requests for rear washer system operation.
The washer fluid level switch may be diagnosed and tested using conventional diagnostic tools and procedures. However, conventional diagnostic
methods may not prove conclusive in the diagnosis of the instrument cluster, the FCM, or the electronic message inputs to or outputs from the instrument
cluster and the FCM that control the operation of the washer fluid visual and/or audible indicators. The most reliable, efficient, and accurate means to
diagnose the washer fluid level indicator, the instrument cluster, the FCM, or the electronic message inputs and outputs related to the washer fluid
indicator requires the use of a diagnostic scan tool.
