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Wiring it up

Like most aftermarket antennas, the RS unit has three leads -- "accessory on" (the orange lead, usually powered directly by a signal from a tuner), unswitched power (red) and ground (black). These are different from the three Mazda leads, and you cannot merely plug them into the wiring harness for the Mazda antenna. The black wire should be easy enough to wire up -- it's just a chassis ground, and I hooked mine up to one of the OEM-turned-Radio-Shack mounting bracket nuts. The red lead must have full time power regardless of whether or not the ignition key is in the accessory or on position. I found a great source nearby the antenna: the hatchback interior light has a full time power lead going into it. If you remove the rear hatch panel, you'll see two wires connecting into the back of the light. The blue/yellow wire (on the light, not on the OEM antenna harness!) is unswitched power -- the switch is a plunger mechanism on the driver's left side of the hatch latching mechanism. Finally, the "antenna up" signal for the orange wire can be used from the blue wire on the original Mazda antenna wiring harness.

As an aside, that blue wire was the most "interesting" part of this whole project. Mazda's OEM antenna is controlled by a relay under the dash. The relay is activated by a fairly common +12v signal from the tuner, but Mazda chose to send a completely different signal back to the antenna, via this convoluted relay. The three wires on the original Mazda antenna wiring harness play a three way shell game between battery positive and battery negative. When the antenna is going up, the blue wire gets battery positive, and the red wire gets battery negative. When the antenna is going down, the red wire gets battery positive, and the blue/yellow wire gets battery negative. So the red lead alternates between positive and negative, the blue wire only sees positive when the stock antenna is supposed to be up, and the blue/yellow wire only sees negative when the stock antenna is supposed to be down. Got that? :) The cool thing is that you don't have to, because most aftermarket antennas have the relay mounted on the antenna, making the wiring logic a helluva lot easier to follow for you and I.

Another little tip: I used tap-in squeeze connectors (Radio Shack part number 64-3053) to connect to these wires without any cutting or soldering. A little electrical tape around the OEM antenna wiring harness would also be a smart idea to keep the hot leads from ever accidentally contacting the chassis. These tips should allow you to retain the stock wiring harness, just in case you or some future owner decides he/she wants to restore the car to totally stock parts.

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