DIY Tachometer Circuit

Written by jack hathcoat
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DIY Tachometer Circuit
Tachometers monitor engine revolutions. (dashboard kilometre rpm image by willem169 from

Tachometers are popular accessories that car enthusiasts and restorers add to enhance driving pleasure and performance. Monitoring engine performance and determining shift-points are features a tachometer add when properly installed. Wiring a tachometer is not difficult because as few as two or three wires are involved; one for power when the key is turned on, one for grounding the tachometer, and one for referencing the engine ignition signal. A wireless transmitter eliminates the engine wire.

Skill level:

Things you need

  • Test light
  • Fuse tap
  • Wrench set
  • Screwdriver set
  • Wire crimps

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  1. 1

    Use a test light and locate a fuse in the fuse panel, normally under the driver's dashboard, that has power when the key is on and no power when the key is off. Install a fuse tap on this fuse and plug the red wire from the tachometer into the tap.

  2. 2

    Locate a suitable area under the dash that is unpainted metal. Find a section that has an existing bolt or sheet metal screw installed. Remove the screw or bolt with a wrench or screwdriver and install the black wire from the tachometer under the screw or bolt. Crimp a suitable connector onto the black wire that will fit your selection.

  3. 3

    Raise the bonnet of the car and locate the ground wire that goes to the ignition coil. In some cases, referencing a service manual is the quickest way to locate the wire. Install the remaining wire from the tachometer by tapping into this circuit. Run the wire from the tachometer through the firewall from underneath the dashboard to the engine compartment to complete the connection. Another option is to install a wireless transmitter. Follow the manufacturer's directions.

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