RAM 2500 Truck 2WD V8-5.7L VIN D (2004)
Washer Fluid Level Indicator: Description and Operation
WASHER FLUID INDICATOR
A washer fluid indicator is standard equipment on all instrument clusters. The washer fluid indicator consists of the words "LOW WASH", which
appear in the lower portion of the odometer/trip odometer Vacuum-Fluorescent Display (VFD) unit. The VFD is soldered onto the cluster electronic
circuit board and is visible through a window with a smoked clear lens located on the lower edge of the tachometer gauge dial face of the cluster
overlay. The dark lens over the VFD prevents the indicator from being clearly visible when it is not illuminated. The "LOW WASH" text appears in
an amber color and at the same lighting level as the odometer/trip odometer information when it is illuminated by the instrument cluster electronic
circuit board. The washer fluid indicator is serviced as a unit with the VFD in the instrument cluster.
The washer fluid indicator gives an indication to the vehicle operator that the fluid level in the washer reservoir is low. This indicator is controlled by
the instrument cluster circuit board based upon cluster programming and electronic messages received by the cluster from the Front Control Module
(FCM) over the Programmable Communications Interface (PCI) data bus. The washer fluid indicator is completely controlled by the instrument
cluster logic circuit, and that logic will only allow this indicator to operate when the instrument cluster receives a battery current input on the fused
ignition switch output (RUN/START) circuit. Therefore, the indicator will always be off when the ignition switch is in any position except On or Start.
The indicator only illuminates when it is switched to ground by the instrument cluster circuitry. The instrument cluster will turn on the washer fluid
indicator for the following reasons:
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Washer Fluid Indicator Lamp-On Message - Each time the cluster receives a washer fluid indicator lamp-on message from the FCM indicating
that a low washer condition has been detected for sixty consecutive seconds, the washer fluid indicator is illuminated and a single chime tone is
sounded. The indicator remains illuminated until the cluster receives a washer fluid indicator lamp-off message for sixty consecutive seconds from
the FCM or until the ignition switch is turned to the Off position, whichever occurs first. The chime tone feature will only repeat during the same
ignition cycle if the washer fluid indicator is cycled off and then on again by the appropriate washer fluid lamp messages from the FCM.
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Actuator Test - Each time the cluster is put through the actuator test, the washer fluid indicator will be turned on, then off again during the VFD
portion of the test to confirm the functionality of the VFD and the cluster control circuitry.
The FCM continually monitors the washer fluid level switch in the washer reservoir to determine the level of the washer fluid. The FCM then sends
the proper washer fluid indicator lamp-on and lamp-off messages to the instrument cluster. For further diagnosis of the washer fluid indicator or the
instrument cluster circuitry that controls the indicator, refer to Instrument Cluster Diagnosis and Testing. For proper diagnosis of the washer fluid level
switch, the FCM, the PCI data bus, or the electronic message inputs to the instrument cluster that control the washer fluid indicator, a DRBIII scan
tool is required. Refer to the appropriate diagnostic information.
