Table of contents: Speedometer pulse sensor ↓ Checking the speedometer pulse sensor ↓ Removal the speedometer pulse… ↓
Previously, we were accustomed to a speedometer that was driven by a flexible shaft - the speedometer shaft. It is completely different in the Audi 100: its speedometer is an electronic measuring device similar to a tachometer. Just like a tachometer, it receives speed pulses - but not from the engine, but from a sensor in the gearbox. The speed of the wheels is measured there. The device correlates the speed pulses with the time factor and thus obtains a reference value for the speed. Due to the lack of a mechanical drive, the trip meter functions partly electrically: the so-called stepper motor turns the drive shaft of the transmission of the meter step by step - depending on the number of speed pulses. The advantages of an electronic speedometer: silent drive, more accurate readings. If the speedometer does not work, you should first check the corresponding fuse in the fuse box.
Speedometer pulse sensor
The speedometer pulses come from the reed switch sensor on the left side of the gearbox. The reed switch is a hermetically sealed contact group located in a gas shell. The contact closes when exposed to a magnetic field. In order for the reed switch to supply pulses, it must close and open in rhythm with the rotation speed. Therefore, the reed wheel rotating in front of the sensor affects the magnetic field that affects the contact group.
Checking the speedometer pulse sensor
Raise the left front wheel.
Press the retaining clip on the sensor plug and remove it.
Connect an ohmmeter to the sensor contacts.
Now slowly turn the left wheel by hand: the ohmmeter readings should fluctuate between 0 Ohm and ∞.
If this is not the case, the sensor should be replaced.
The rear housing cover (2) is removed from the instrument panel (1). The housing cover contains the printed circuit board (control device) for Mini-Check system (mini-checks), auto-check systems (autochecks) or on-board computer.
Disassembled combined instrument panel:
1 - main plate;
2 - on-board computer with automatic check system;
3 - fuel quantity indicator;
4 - tachometer;
5 - speedometer;
6 — button for setting the daily distance meter.
Removal the speedometer pulse generator
Press the retaining clip on the sensor plug and remove it.
Lightly press down on the latch on the mounting bracket and turn the sensor slightly to the right.
Pull the sensor out of the gearbox.
When installing, pay attention to the correct fit of the rubber sealing ring.