Refer to my pin-out table for Subaru's 20-pin harness. Column "A" shows the wire colors on my harness.
Connect each wire to the corresponding wire on your new head unit's power/speaker harness. Although the colors should match, read your HU's installation manual to verify the function of each wire.
If your installation will include a steering wheel interface
module (Axxess ASWC or PAC Audio SWI-JACK, SWI-PS, etc.), remember that
you will also be
connecting several wires from the interface module. In some cases,
you'll need to join a group of 3 or even 5 wires. Read through
all of the instructions before starting your installation.
How To Connect Wires
The best method to join wires is soldering. This gives the most compact and reliable connections. When joining two wires, spiral the ends around each other with the wires pointed towards each other, as shown in this picture.
If you're using heat-shrink tubing to insulate the connections, use tubing sized for each particular junction (you may need slightly larger diameter tubing when joining larger wires). Remember to slide the tubing on before you begin twisting the wires together.
If crimping, insulated butt-splice terminals are best. For each junction, use a crimp terminal of appropriate size for the number and gauges of wires that you're joining.
Soldering is strongly recommended for the steering wheel control (SWC) wires. T-taps (or "vampire" taps) are a bad idea.
Watch out for the wires with stripes — the stripes are narrow and easy to miss. It helps to work in bright light (daylight is best).
Insulate the ends of all wires (separately) that you don't use — on my 20-pin harness, your HU's harness, and the steering wheel control interface's harness.
Ground Wire (Black)
Many HU manufacturers put a screw terminal lug on their Black wire, since some car harnesses don't have a ground wire (so grounding to the car's chassis is the only option). Since Subarus do have a ground wire on the radio harness, I recommend that you cut off the HU's terminal lug and solder or crimp that wire to the bare end of the Black lead on my harness.
Constant Power Wire (Yellow)
Some Clarion HUs (and possibly other brands) have two Yellow power wires on the main power/speaker harness. One or both wires may have an in-line fuse holder. You will need to connect the ends of both wires to the Yellow wire on the 20-pin harness. Do not remove any fuse holders.
Power Antenna Wire
Your Subaru has an antenna booster amplifier, which is powered from pin 9 on the 20-pin radio harness (Blue wire on my installation harness). You must connect this wire to a source of +12V or your AM/FM radio will get very poor reception. Options, from 'best' to 'worst':
See footnotes (K) and (L) on my Subaru 20-pin pin-out page.
Some HUs may have a Blue wire, a Blue/White wire, or both. A
few HUs don't have either wire. Check your HU's installation
If your HU only has a Blue/White wire, it is OK to use that
for both your Subaru's power antenna and the turn-on signal for speaker
amplifiers. HUs will have a maximum current rating that they can
supply on this output (typically 250 or 300 mA). Check your HU's
and amplifier's documentation (or ask the manufacturers) to make sure
you don't exceed that rating. A Subaru's antenna booster draws
about 50 mA.
Tip: If you are also installing an accessory device that connects to the AM/FM antenna (such as a traffic data receiver or TV), you may want to connect pin 9 to +12V Accessory so that the device can get reception even when you turn off your HU.
Illumination Control Wire
Most HUs have a wire to control the brightness of their illumination. The dimming is two-stage: The HU will be at full brightness during the day, and slightly dimmed when you turn on your car's headlights.
If your HU has a wire for "Dimmer" or "Illumination Control," connect that to the Orange wire (pin 1, Illumination +) on the 20-pin harness.
No HU that I'm aware of today wants to see a variable voltage
on its illumination control wire — the HU's backlights are not
able to vary gradually in tandem with your car's instrument dimmer knob.
The HU's wire may be Orange or Orange/White. However, some HUs have no dimmer wire at all — some have no dimming capability, and other recent models use an ambient light sensor or GPS time and location. A few HUs even have an Orange/White wire that is not for illumination. Check your HU's installation instructions!
On HUs that have a dimmer wire, most also have a related menu option for "dimming." Be sure to enable that option (set it to detect the voltage on the dimmer wire). See your HU's user manual for details.
CAN Data Bus Wires
I'm not aware of any aftermarket HU that can connect to these wires. If your harness has these wires, insulate the ends (individually).
If you're keeping your stock HU and using a pair of forward/reverse harnesses to connect other aftermarket gear, join the respective CAN wires between the two harnesses (pin 11 to 11 and 12 to 12). The pair should be twisted. Tip: Join the CAN wires first (before any others) and then twist the two harnesses to twist these two wires. Then continue joining or making your connections to the remaining wires (power, speakers, etc.).
Connecting SWC Interface Module To Car
Since my 20-pin harness includes the SWC wires, you won't need to tap into your car's factory wires. In general, you will make the following connections:
You'll need to make additional connection(s) between the module and your HU's "wired remote control" input.
Connecting the Axxess ASWC Module
Please see this guide for additional instructions to install the Axxess ASWC steering wheel interface.
I now have the Axxess ASWC steering wheel interface modules available. E-mail me for details.
© Copyright 2011 by David Carter. All rights reserved.