Oil pressure and water temperature are probably the most important things to monitor in a racecar, and if you’re allowed to play with air/fuel ratio, a wideband gauge is a must.
We reached out to AEM Electronics in Hawthorne, Calif., which supplied three gauges for a new Spec Miata build. The idea was to do a bulletproof installation, do it right the first time, with no need to go back under the hood or dash to correct something we missed.
We succeeded on that front and learned a lot along the way, the first of which was the importance of a common power source and a common ground. We’ve worked on cars in the past where each gauge was wired to a different power source and grounded ostensibly wherever the installer could find negative earth.
We picked up a six-way blade fuse box from Amazon for $9.25. It has four holes for mounting it, though we really only needed one, a common power pole for all six male blade connections, receptacles for blade fuses and LEDs that indicate a blown fuse. We had to supply the 5-amp fuse for each gauge.
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Using that fuse panel, we could power it once, then run all three gauges from it. A simple, centralized power source. For a ground, we ran a leftover factory bolt through metal frame on the dash that bolted to the chassis. That provided the negative earth we needed to ground all the gauges, which all have a ground wire.
It’s important to note that the AEM gauges have a lot of extra wiring for use with things like the AEM Infinity controller or data logger, so we had to “cap off” the other wires so they wouldn’t accidentally touch something metal and go to fritz.
The installation couldn’t have gone any better. The directions AEM included were essential, and they were presented in a way that made things simple and easy to understand. Here’s how the installation unfolded.