GF54.30-P-4001Q Coolant/Washer Fluid Level Voltage Coding, Function

GF54.30-P-4001Q Coolant/washer Fluid Level Voltage Coding, Function

Component Identification:

Voltage coding
The coolant level indicator switch (S41) and windshield washer fluid level indicator switch (S42) are connected in parallel for voltage coding of the resistances (the values must differ).
These resistors form, when the coolant level indicator switch (S41) and windshield washer fluid level indicator switch (S42) is open, together with "r3" from the front SAM control unit with fuse and relay module (N10/1), a voltage divider which is supplied with the constant voltage "u".
The voltage "u e" at the input of the front SAM control unit with e fuse and relay module (N10/1) is therefore dependent on the positions of the coolant level indicator switch (S41), the windshield washer fluid level indicator switch (S42) and the values of the resistors "r1, r2".

With the coolant level indicator switch (S41) and windshield washer fluid level indicator switch (S42) a total of 4 combination options of switch conditions of the coolant level indicator switch (S41) and the windshield washer fluid level indicator switch (S42) result (see table).
Each of these combinations produces a different voltage value "u e" at the input of the front SAM control unit with fuse and relay module (N10/1).

Evaluation
The voltage "u e" is applied at the input of the Analog-Digital- e Converter (ADC) in the front SAM control unit with fuse and relay module (N10/1) an. The analog-to-digital converter (ADC) converts the analog voltage into a digital value. This is necessary as the processor of the front SAM control unit with fuse and relay module (N10/1) can only work with digital values.
The processor compares the values applied with the threshold value stored in a memory and if necessary places the corresponding Controller Area Network (data bus/CAN bus) (CAN) message "Coolant level too low" or "Washer fluid level too low" on the Controller Area Network bus Class B (interior) (CAN-B). The instrument cluster (A1) reads these CAN messages and actuates the multifunction display (A1p13) for the picture and the text accordingly.

These warning messages can be acknowledged with the instrument illumination rheostat and reset button (A1r1) on the instrument cluster (A1).

With the known resistance values and known voltage "u" "u e" can be calculated with the following formula:

Ue=u X (r1+r2) + (r1+r2+r3)

The above table shows the assignment of the switch conditions of the coolant level indicator switch (S41) and windshield washer fluid level indicator switch (S42) to the warning messages.