Installing a Tachometer or Water Temp Gauge

By Speedway Tech Team

  Created 2014

Installing a tachometer or water temperature gauge has multiple benefits. First and foremost, not everyone has a finely calibrated ear for monitoring the RPM’s of your vehicle. And let’s face it, none of us is interested in having a finger on the engine to monitor temperature.

Thankfully, installing a tachometer or water temperature gauge is not very involved or complicated. You won’t even need very many specialized tools to get the job done, hand tools will suffice. The folks at Autometer put together a couple quick videos explaining what wire goes where, and why.

Installing a tachometer on a vehicle with a standard ignition system is a pretty easy process. On the harness there will be four wires, red, black, white, and green. The red wire is linked to a key-switched ignition source, to transfer power to the tachometer. Black, as is usually the case, is the ground. It is recommended that this be attached to a solid engine or chassis ground. Do this wrong, and you risk ruining the tachometer you were installing. The white wire is for the illumination of the tachometer, so that will be attached to the headlight switch of your vehicle. Make sure to tie it in to the power side when the switch is engaged, this will power the light on the tachometer at the same time as the rest of the lights on the dash. The green wire is your signal wire, which will be routed out to your ignition coil and attached to the negative side. You can also run the wire to the tachometer output terminal on an ignition control box if you have one.

Installing a water temperature gauge is just as simple as installing the tachometer was, regardless of whether you are installing a mechanical gauge or an electrical gauge. You’ll need to tap into a key-switched power source again, as the water temperature gauges are externally powered. Grounding is the same, follow the same guidelines listed above and have a good ground to either the engine or the frame. Lights on the gauge are the same, you will need to tap into the headlight switch output to ensure the lights on your water temperature gauge illuminate with the rest of the dash lights. Lastly, the sending unit, which could either be a standard short sweep electric gauge sender, or a full sweep electric gauge. The sending unit will be installed in an open water port on the intake manifold, cylinder head, or a water neck.

Related Articles:

• Ammeter and Voltmeter Replacement
• How to Ground the Electrical System
• Mechanical vs. Electrical Gauges