Tachometer: Description and Operation
Instrument Cluster:
Tachometer
Tachometer indicates engine speed in rpm (revolutions per minute) with engine running. A wire to "TACH" connector on ignition module measures ignition pulses of module. An electronic circuit on tachometer converts these pulses to rpm data.
CAUTION: When removing or installing any electrical units, disconnect negative battery cable to prevent possible short circuits which could lead to personal injury and/or property damage.
When replacing odometer assembly, law requires odometer reading of replacement unit to be set to same mileage as prior odometer. If mileage cannot be set, law requires that replacement odometer be set at zero and a label be installed on driver's door frame to show previous odometer reading and date of replacement.
Circuit Operation
A solid state circuit controls the tachometer. With the engine running, ignition coil pulses proportional to engine speed are read into the solid state circuits, which output the engine speed in RPM through the tachometer.