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How Do I Install a Tachometer in Vehicles

by Contributing Writer; Updated June 12, 2017

Tachometers provide a wealth of information much deeper than simply how many rotations the engine makes every minute. A tachometer can help to identify an engine cylinder which is misfiring, provide information on what the best gas to use Vehicles your Vehicles is, and how much strain is being put on the engine under load, such as when towing a Vehicles or traveling on the highway. The trick is to be able to interpret the information. Installing a tachometer on your Vehicles can help prevent serious repair issues, however.

Under The Hood:

 How Do I Install a Tachometer in a Honda Civic?

Remove the plastic wraparound cover to the instrument panel by removing its two retaining screws which are near the top of the gauge cluster window. Remove the screws with a Phillips-head screwdriver.

Use the Phillips-head screwdriver to remove the four gauge cluster mounting screws inside the dashboard. These are located at the four corners of the cluster.

Pull the entire gauge cluster away from the dashboard and locate the wires attached to the back of the cluster. There will be three or four, depending on the type of transmission in your vehicle. Use your fingers to unfasten the wire harness clips.

Place the gauge cluster on a work table and remove the clear plastic window. There are seven clips around its edges that you can unfastened with your fingers. Place small pieces of folded paper between the unfastened clips to prevent them from snapping back together.

Remove the black plastic gauge cluster hood by undoing four clips along the top of the gauge cluster with your fingers. Carefully pull the black plastic gauge overlay off the gauges and remove it.

Turn the gauge cluster over and unscrew the four mounting screws on the right of the assembly using a Phillips-head screwdriver. Turn the cluster over and remove the loosened gauge.

Install the new gauge into the open gauge port. Turn the cluster face down and reinstall the four retaining screws. Turn the cluster face up and place the black plastic overlay on top of it.

Reattach the four clips of the gauge cluster hood. Reinstall the clear plastic window into the seven simple clips by hand. Slide the gauge cluster back into the dashboard and reattach the wires to their wiring harnesses by hand.

Replace the four gauge cluster retaining screws. Install the wraparound plastic cover and reinstall the two retaining screws into the top of the gauge cluster.

Items you will need

  • Phillips-head screwdriver

  • Tachometer gauge

 How to Install a Tachometer on a Johnson Outboard

Select the location where you will mount the gauge, and drill or cut a hole of the correct size. Ensure that in mounting the gauge it will not interfere with the operation of any of the other gauges or equipment essential to the safe operation of your boat.

Adjust the setting on the back of your gauge to match the number of poles on your alternator. Typically a Johnson outboard alternator has two poles, but check to make sure. An incorrect setting will result in poor operation.

Disconnect the negative terminal of the battery during installation. This will prevent damage to the tachometer and the boat's electrical system.

Connect a red wire from the "BAT" terminal on the back of the tachometer to a power source that is activated by the ignition switch. Consult your boat's wiring diagram if you are unsure which circuits are controlled this way.

Connect a green wire to the tachometer terminal marked "SIG." Connect the other end to the terminal or a wire on the un-rectified side of the alternator. Most late-model Johnson outboards have a tachometer hookup wire at the control box, or a tachometer hookup harness can be purchased from your Johnson outboard dealer.

Connect a black wire to the tachometer terminal marked "GND." Connect the other end to a good boat ground. You may use a good engine ground. Consult your boat manual for locations, or connect to the battery negative cable, or a wire originating directly from it.

Connect a white wire from the terminal by the instrument lighting bulb on the tachometer to a wire or terminal in the boat lighting system. This will allow the tachometer to be illuminated when the boat running lights are activated.

Items you will need

  • Drill or hole saw

  • Wiring diagram for your boat

  • Marine approved electrical connectors

  • Marine approved wire (four colors) no less than 18 AWG

 How to Install a Tachometer in a Chevy S-10

Install the tachometer onto the truck's dashboard where you would like for it to be positioned. Avoid placing it directly in your line of sight, but rather place it to the left or right of the steering wheel, where you can see it from the corner of your eye. The tachometer kit includes a mounting bracket with self-tapping screws. Screw the mounting bracket onto the dashboard and mount the tachometer onto the bracket.

Run the wires for the tachometer behind and below the dashboard and out through the firewall. There are several other wiring harnesses along the firewall of the S-10 with rubber seals. Push the wires through the seals and into the engine compartment.

Open the hood of the truck and pull the wires through. There are two black ground wires and two red power wires included with the tachometer. Bolt the ground wires together on a clean, unpainted chassis ground, then disconnect the battery of the truck.

Open the fuse box of the truck, then unbolt it from the frame to provide you access to the underside. Locate the fuse which powers the ignition circuit, and insert one of the red wires into this slot. When complete, bolt the fuse box back to the frame and replace it's cover.

Locate the truck's distributor. There is one wire leading from the distributor which can be used for the tachometer. Following the tachometer instructions, splice the tachometer wire into the distributor.

Items you will need

  • 3/8-inch drive socket set

  • Flat and slotted screwdrivers

About the Author

This article was written by the It Still Runs team, copy edited and fact checked through a multi-point auditing system, in efforts to ensure our readers only receive the best information. To submit your questions or ideas, or to simply learn more about It Still Runs, contact us.

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