Checking the coolant temperature and fuel level gauges (Audi 100 C3)

Incorrect operation of the coolant temperature and fuel level indicators may be due to a lack of supply voltage to the voltage stabilizer, which is installed on the back of the instrument cluster, on the left side of the printed circuit board.

First of all, check the presence of voltage supply to the stabilizer by connecting a voltmeter between its input and the "ground", the value of which should be almost equal to the voltage of the battery.

Then measure the output voltage of the stabilizer between the "ground" and its output, which should be within 9.75-10.25 V. If the obtained output voltage does not correspond to the norm, replace the voltage stabilizer.

Fuel level indicator

If the device malfunctions, check the sensor installed in the fuel tank for proper operation. To do this, never connect the indicator wire directly to the "ground". The check is performed by connecting a resistor between the two plugs of the sensor connector.



When a 544 Ohm resistor is connected, the pointer should be at the beginning of the scale (the "empty tank" position), and when a 60 Ohm resistor is connected, it should move to the end of the scale (the "full tank" position). Each of these positions of the pointer is marked on the scale with two dots indicating the tolerance. If the pointer does not occupy the same position relative to the marks at the beginning and end of the scale, adjust the pointer as indicated below. If this can be done, replace the sensor. If the difference in the position of the pointer between the marks remains significant, check the supply voltage of the device and, if necessary, replace it.

Adjusting the fuel gauge

Fill the completely empty tank with 12 liters of fuel. Turn on the ignition (and do this at least 2 minutes before adjusting the pointer): the arrow should be on the right edge of the red zone of the scale. If not, adjust the device with the adjusting screw underneath it.