Washer Fluid Level Indicator: Description and Operation

GF54.30-P-3030GH Displaying Washer Fluid Level, Function

Function requirement:
Engine: ON

Function
If the fluid level in the washer fluid reservoir drops below the minimum level (1/3 capacity), the low windshield washer fluid level indicator lamp (A1e13) in the instrument cluster (A1) lights up.

To detect the windshield washer fluid level, the instrument cluster (A1) is connected direct with the windshield washer fluid level switch (S42) over two cables. This switch consists of two electrodes.
- When the fluid level is correct, both electrodes are immersed in the washer fluid. The fluid acts as a dielectric between the electrodes.
- When the fluid level is below the minimum mark, the electrodes of the switch are no longer immersed in the washer fluid. The only dielectric between the electrodes is air.

Evaluation
The instrument cluster (A1) sends test pulses of one millisecond duration to the switch. These pulses are distorted differently depending on the dielectric (air or washer fluid).

The instrument cluster (A1) evaluates the pulse form and actuates the low windshield washer fluid level indicator lamp (A1e13) a waiting time of approx. 60 seconds after when the level is below the minimum (the electrodes are entirely surrounded by air).

The waiting time is necessary for an exact measurement, otherwise the warning lamp could start to flicker when cornering or driving off-road.