Tapping Into the Factory Audio System

By Bill "BillaVista" Ansell
Copyright 2018 - Bill Ansell
(click any pic to enlarge)


The old days of ripping out a lackluster factory stereo and replacing it with your choice of head-unit, amps, and speakers are long gone. Today, so-called "infotainment" systems consist of multiple networked systems communicating across networks to control everything from GPS navigation, to wireless communication, internet access, warning systems, and of course music from a number of different systems. In addition, many modern "head units" include large touch-screen displays in unique and often propietary configurations - meaning simple removal and replacement is just not feasable. The days of DIN and double-DIN standard form-factors are long gone.

What does this mean? It means we pretty much have only one option for upgrading audio components - and that is tapping into the factory system's speaker outputs and running them into either a Line Out Converter (LOC) that converts speak outputs to low-level RCA signala, or an amplifier or digital signal processor capable of accepting high-level (i.e. speaker) inputs. Fortunately there are a huge number of quality components available today that can indeed accept high-level inputs. First though, we have to tap into the factory system.

This quick article shows you how to do that on the Right-hand-drive 2017+ FIAT 124 Spiders with standard (non-Bose) stereo system.

NOTE: At the bottom of this article are some PDF files that include the wiring diagrams for both the Bose and the Basic (no 7" display screen) systems, both of which are different from the 7" non-Bose system illustrated in this article. Users with those systems will be able to glean the required information from those files.

DISCLAIMER: This info (i.e. wiring diagrams etc.) is taken from the 2016 Mazda MX-5 (Miata) workshop manual. I am fairly confident it is identical to the Spider since the cars are built on the same line in the same plant by Mazda, but you should verify for yourself first.

The factory system uses a component known as the "Tuner Amplifier Unit" or TAU. It is from this component that the wires go to the speakers.

The TAU is located on the right-hand side of the right footwell, as shown here.

The specific connector that contains the speaker wires is 0920-202B.

A view of the TAU location.

This is a diagram of connector 0920-202B.

The ports/pins of interest are as folllows:

2A - Yellow wire with black stripe - Left speaker (+)

2C - Yellow wire with green stripe - Left speaker (-)

2D - Yellow wire - Right speaker (+)

2F - White wire with black stripe - Right speaker (-)

Wiring diagram showing the left speakers (highlighted by the red box)
Wiring diagram showing the right speakers (highlighted by the red box)

This diagram shows how to read the colours of the wires from the wiring diagrams.

Two–colour wires are indicated by a two–colour code symbol.
The first letter indicates the base colour of the wire, the second indicates the colour of the stripe.



This article will be updated as I dig into the system more, but it should get you started.








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