A tachometer is a device that measures the rotations-per-minute created by an automotive engine. Most tachometers measure the rate at which the ignition system sends pulses of electricity to the spark plugs in the engine. Many modern ignition systems include a tachometer signal port; older, point-type ignition systems do not. The tachometer must be connected to the negative coil of the distributor on the latter system.
Connect the power wire from the tachometer's wire harness to the accessory power port on the ignition switch.
Connect the ground wire from the tachometer to a ground point on the vehicle's chassis; use the ground clamp. If your tachometer has a case ground, attach the ring harness of the case-ground-wire to the post of the ground clamp's thumb nut.
Connect the tachometer signal wire to the negative side of the distributor coil. The negative side will be marked with a "-" sign, or the word "TACH" or "DIST."
If your tachometer has a switch wire, attach it to a 12-volt power port on the ignition system's wire harness.
