Grand Cherokee 2WD V8-5.7L VIN 2 (2005)
Washer Fluid Level Switch: Description and Operation
The washer fluid level switch is located on the left outboard side of the washer reservoir (5), near the windshield washer pump. The washer fluid level
switch is a single pole, single throw reed-type switch. Only the molded plastic positioning flange (2) and the integral connector receptacle (1) are visible
when the switch is installed in the reservoir. A seal flange with a large barbed nipple (3) on the switch housing passes through a rubber grommet (6)
installed in the dedicated switch mounting hole of the washer reservoir.
A small, molded plastic float (4) with two pivot pins is attached to the stanchion (7) that extend toward the float from the nipple. 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 faulty or damaged, it 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 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 and the front washer pump motor control circuit of the front control module (FCM).
When the switch closes, the FCM senses the ground on the washer pump motor control 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 steering control module (SCM), FCM or the electronic message inputs to or outputs from the
SCM 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, SCM, FCM or the electronic message inputs and outputs related to the washer fluid indicator requires the use
of a diagnostic scan tool.
