Back in April of last year, the speedometer failed in my ‘94 Explorer. Rather than hunting down a replacement cable and tearing apart the dash just to restore an old analog needle, I opted to build a digital replacement using a Raspberry Pi and GPS.

BOM (~$100)

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The Build

I kept the physical build simple. I discarded the top of the Pi case and used a Dremel to clear space for the HDMI bridge that links the LCD to the Pi.

Software-wise, I flashed Raspbian, installed Navit for the mapping and data visualization, and hooked up the hardware. Out of the box, Navit provides a solid base for speed and GPS data.

Raspberry Pi running Navit

Installation

To make it a permanent fixture, I configured the Pi for automatic login and set Navit to launch at boot.

I used Command strips to adhere the unit to the center of my dashboard—sturdy enough for bumpy roads but easy to pull if I need to update the SD card. I ran the magnetic GPS receiver to the underside of the roof for clear signal and tapped into an ignition-switched power source behind the dash.

Pro-tip: If you wire yours to an always-on source, use an inline switch. These things will cause a parasitic leak and kill your battery if left sitting.

Raspberry Pi in Use

The Result

I eventually customized the Navit XML configuration to make the MPH readout much larger and more readable.

The Explorer

Is it sexy? Not really. But it solved a mechanical failure in an afternoon with modern parts. GPS lock usually happens within 15-30 seconds—far more reliable than the cheap standalone digital speedometers I tested first.

It’s been a perfect replacement for a 30-year-old plastic cable.