Instructables
Picture of How to install a tachometer
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In this instructable I will show you how I installed an aftermarket tachometer on my ‘91 Chevy S-10. Tachometers are a great tool for your vehicle if you enjoy monitoring your engine speed or idle. In fact, they are nearly a necessity for a vehicle with a manual transmission. 
 
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Step 1: Parts & Tools

Picture of Parts & Tools
Parts:
Tachometer - - - - - Can be purchased from most any auto parts store for as low as $33. Mine was salvaged from my old truck
3M quick splice connectors 14-18 gauge - - - - - $4.10 (Walmart)

Tools: 
Wire cutters
Wire strippers
Automotive diagnostic tool-used for finding tachometer wire 
Ratchet and sockets
Screwdriver
Drill


Step 2: Tachometer input wires

Picture of Tachometer input wires
The following are the wires going into the tachometer.

Red- ignition power
Black- ground
White- illumination power
Green- tach wire

Step 3: Finding the tach wire

First I found the output from the distributor cap. My distributor is hard to get to, so I had to remove a couple wire braces to reach it. Other than being almost out of reach, finding the correct wire was fairly easy.

Step 4: Using the tach meter

Picture of Using the tach meter
To be sure I had found the right wire, I used this diagnostic tool. I connected the black wire to the (-) side of the battery and the red to the (+). Next I clipped the meter wire onto the white wire from the distributor. To be sure it was the right one, I had someone watch the meter as I revved the engine. 

Be sure to mark or remember the wire for when you come back later.

Step 5:

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Next, I found where I wanted to mount the tach, and removed a dash panel to access the wiring behind it. I chose to place the tachometer behind and below the ignition, where it would be out of the way yet I could easily see it.

Note; When I was working on this project, I also installed a new stereo and rewired my instrument panel lights that had not been working.
rey_salasjr24 days ago

what about diesel engine?

mikaleda1 year ago
You need to install a rubber grommet where the wire goes through the firewall so it doesn't cause a short. The way you are running it is dangerous it could start a fire if the wire were to short out.
Harvard821 year ago
You really should add a grommet between the wire and the firewall or else vibrations will cause the firewall to cut the sheathing and make issues later.