How to wire-up a Tachometer

I was scrounging around the wreckers, looking for late model factory gauge packages and came across a 1983 Olds Cutlass wagon with a complete gauge package in it including a 0-6000 rpm Tach. It was strange to see in a family wagon with fake wood paneling on the side. Since I live in Canada, the speedo and oil pressure are in metric units but I'm sure the same gauges exist in the States in Imperial units.

What is really nice about these gauges is that they are small - the tach is only 3" in diameter. It should be able to fit into the existing opening in the dash.


Here's the layout after disassembling the dash package, notice the PRND21 on the tach!


The PRND21 is on the tach and connected to the steering column by a small wire

A really neat feature which should solve a lot of problems for some people is the PRND21 indicator that's on the bottom of the tach. It is connected to the steering column shifter by a clip. Incredibly simple and it is also detachable for those who don't need to use it like me.


Here's the back of the tach - notice the jumper for either 6 or 8 cylinder engines.

On a HEI distributer there are only 2 wires used plus chassis ground

To connect the tach to the distributer, connect the tach's coil wire to the distributer's tach wire. Here's a desciption of the tach wires:

  • +12V and Ground

    • connect the +12V to the ignition switch ON position
    • use 18 ga wire
    • connect the ground to a good ground point - chassis would work

  • Tach Coil connection

    • connect to the HEI Tach line - on my distributor it is the black wire connected with a white connector to distributor in the previous picture
    • use 18 ga wire

If this page has helped you, please consider donating $1.00 to support the cost of hosting this site, thanks.

Return to

Copyright July 2011 Eugene Blanchard