This page describes the pin layout of the connectors on 1990-1994 Subaru Legacy stereos. This information is partly from the factory service manuals and partly from my own poking around, so no warranty is provided.

These are the two connectors on the car's wiring harness:

Harness connector image

The 7-pin one carries power distribution:

Pin Description Wire color (Main/Stripe)
1 Accessory +12v
2 Illumination (+)
3 Battery +12v
4 Ground
5 Illumination (-)
6 Power antenna control
7 Not connected

The 9-pin one carries speaker signals:

Pin Description Wire color (Main/Stripe)
1 Front Right (+)
2 Front Left (+)
3 Rear Left (+)
4 Rear Right (+)
5 Front Right (-)
6 Front Left (-)
7 Accessory +12v
8 Rear Left (-)
9 Rear Right (-)

The illumination control works like this: when the headlights are off, both illumination lines are floating. When they are turned on, "Illumination (+)" has +12v on it and "Illumination (-)" is varied between 0 and 12 volts by the illumination control unit to achieve dimming. If you need to convert this signal to the more common system with a fixed ground, look at this page.

Note: Earlier versions of this page had the two illumination wires reversed. Thanks to SVXdc for noticing.

The head unit itself also has a 13-pin DIN style connector on the back for a CD player. This diagram is drawn while looking at the back of the head unit:

CD player connector image

Since the front-mounted AUX IN connector was deleted in 1992, this connector is useful as an auxiliary input for things like handheld MP3 players.

TRG is the trigger line; to switch the radio from radio mode to external-input mode, apply +12v to this line.

COM is the common line shared by the left and right inputs, and L and R are the line-level inputs.

This information about the 13-pin DIN connector was determined on a Panasonic head unit, and hasn't been tested on a Clarion one. It is likely the same, but I can't guarantee it.

This 13-pin DIN style connector may also be the same as the connector on other Panasonic or Clarion stereos.