Speedometer Head: Description and Operation

Circuit Description
When the ignition switch is in the ON or START position, battery voltage is applied to the gauges (speedometer, tachometer, fuel gauge and engine coolant temperature gauge) from fuse 28.

Speedometer
The speedometer drive circuit receives pulses from the vehicle speed sensor (VSS). The pulse rate increases as the car accelerates. The frequency and duration of these input pulses are measured and displayed by the speedometer.