The first cruise control system I installed on an MX-5 is on an NBFL—namely, mine. Once that installation was a success, it seemed like a fun challenge to pull it off on a European NA MX-5 as well. For that, I looked for a volunteer who didn’t live too far from me, because it would require a lot of research. To be honest, much more research than I had expected. I’d now go so far as to say that, in that generation, the American Miata differs enormously—both electrically and mechanically—from the European NA MX-5,
The NA Miata was released with an airbag and a thicker steering column right from the start. The combination switch had curved levers, while the NA MX-5 was equipped with a combination switch that had straight levers. The most important difference is that on the NA MX-5, the full power for the lights goes through that combination switch, whereas on the NA Miata, everything was switched via relays.
Does this mean you can’t use the original cruise control system on a European NA MX-5? No, but you can’t use the original lever on the steering wheel. However, there’s a simple solution for this: use a flash-off-flash switch—a small switch that you can mount on the cover around the combination switch to take over the lever’s functions.
While you might expect to find wiring for cruise control in an American Miata, you won’t find any in a European NA model. The entire wiring harness for the system must be added. In addition to a standard Miata kit, a component must also be added to the instrument cluster. This is because the cruise control module requires information about the car’s speed. In American instrument clusters—as well as in those for cars with automatic transmissions—a reed switch is installed for this purpose. The reed switch alternates between making and breaking a conductive contact, depending on the presence or absence of a magnetic field. Inside the odometer is a component containing a magnet. This component is driven by the odometer cable. As the car travels faster, the contact is made and broken more frequently. The signal generated is a square wave that alternates between 0 and 5 volts, allowing the cruise control module to determine how fast the car is traveling.
Other than that, the parts you need are the same as for the American Miata. If you buy a set of parts, try to have the connectors included as well. You’ll need them to assemble the wiring harness.
The first generation didn’t have a cruise indicator—by that I mean a light that shows whether the car is currently using cruise control or not. Of course, you can tell by the feel of the car, especially the gas pedal, but I don’t think a light like that is an unnecessary luxury. It’s possible to build your own cruise indicator so you can see in the instrument cluster that the system is active. This uses a number of signals from the cruise control module. In previous projects, I’ve added a green LED, as shown in the photo below.
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