Crux SWRAD-55 Wiring Interface

Connect a new car stereo and retain the factory amp and steering wheel audio controls in select 2001-10 Audi models

Item #: 249SWRAD55

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Wire in a new radio

Crux's SWRAD-55 interface ensures that you can keep the steering wheel audio controls and the factory amplifier in your Audi when you replace the original radio. Connect this interface to the wires on your new car stereo's wiring harness, and you've covered the power, ground, and factory speaker connections for your new stereo.

The SWRAD-55 interface also offers the reverse, illumination, and Vehicle Speed Sensor (V.S.S.) outputs that you'll need if you're installing a navigation receiver. The Crux interface works with either amplified or non-amplified factory systems. See Details for a list of compatible car stereos.

Note: Most vehicles will require additional installation parts — please identify your vehicle if you haven’t done so, then check here for a list of parts. You can also call an Advisor for more information.

Product Highlights:

  • connect a new stereo in select 2001-10 Audi models
  • retain your steering wheel audio controls and factory amp (if present)
  • provides Vehicle Speed Sensor (V.S.S.), reverse gear, and illumination connections for installing navigation receivers
  • warranty: 1 year
  • Our 60-day money-back guarantee

Hands-on research

What's in the box?

Download owner's manual

  • Radio replacement interface module (for Audi)
  • 2 Wiring harnesses
  • 2 SWC harnesses
  • Installation Instructions

Product Research


Audi Radio Replacement Interface: The CRUX SWRAD-55 is a radio replacement interface for select 2001-2010 Audi vehicles. It facilitates the integration of an aftermarket radio to enable retention of factory features when replacing a factory installed radio in select Audi cars. This interface is also pre-programmed for retention of steering wheel controls.

Compatibility: The CRUX SWRAD-55 is supported by the following 2001-2010 Audi vehicles; with non-amplified or amplified factory audio systems (including Bose).

Make Model  Year
Audi A3 2002-2010
A4 2001-2008
A5 2008-2010
A6 2002-2004
S4 2004-2008
Q5 2002-2010
TT 2002-2010
Note: Please consult Crutchfield's Outfit My Car to see if your vehicle is compatible and what additional installation accessories will be needed.

Steering Wheel Control Retention: The CRUX SWRAD-55 also features a steering wheel control output for Alpine, Clarion, JVC, Kenwood, Pioneer, and Sony aftermarket head units. The steering wheel control output consists of a right-angle 3.5mm connector and a light blue/yellow wire (use the connection that your aftermarket head unit is fitted with). The SWRAD-55 interface module will work with any of the listed aftermarket head units, by setting its three dip-switches (see owner's manual for appropriate setting).

Note: The steering wheel control harness features two 4-pin connectors (labeled - Pioneer/Sony and Alpine/Clarion/Kenwood/JVC). You will only plug in one of these connectors to the interface module, based on the type aftermarket head unit you are installing.

Navigation Outputs: The CRUX SWRAD-55 radio replacement interface module provides a VSS (vehicle speed sense) and a Reverse Gear output to make installing an aftermarket Navigation radio simpler and less time consuming.

Amp Turn-On: The CRUX SWRAD-55 provides an amplifier turn-on lead for your vehicle's factory amplifiers (if equipped). Make sure to connect this wire if your vehicle features a factory Bose system or factory rear sub.

Wiring Harness: The SWRAD-55 includes two wiring harnesses; there is a 3-connector factory harness (20-/8-/8-pin) and a 1-connector (44-pin) factory harness. Only one will be used based on the type of factory plug behind your radio. Each harness also features a 12-pin connector that plugs into the SWRAD-55 interface module. The wiring harness also provides bare-wire leads (power/ground, speaker, illumination, turn-on, and navigation) which will need to be hardwired to your aftermarket head unit's wiring harness. In addition, RCA connectors are provided for vehicles with factory amplifiers. These RCA connectors plug into the RCA preamp-outputs on the back of your aftermarket head unit.

Wire Color Function
Black Chassis Ground
Red +12 Volt Accessory
Yellow +12 Volt Constant
Orange Illumination
Blue Amp Turn-On
White Left Front Speaker +
White/black Left Front Speaker -
Gray Right Front Speaker +
Gray/black Right Front Speaker -
Green Left Rear Speaker +
Green/black Left Rear Speaker -
Purple Right Rear Speaker +
Purple/black Right Rear Speaker -
Purple/white VSS (vehicle speed sensor)
Red/white Reverse
White RCA Left Front Speakers
Gray RCA Right Front Speakers
Green RCA Left Rear Speakers
Purple RCA Right Rear Speakers
Notes: Speaker and RCA connection will depend on what type of factory audio system you have in your vehicle.
  • For Non-Bose Systems: Connect the eight speaker wires of this harness to the front & rear speaker wire leads of your aftermarket head unit's wiring harness (RCA-connectors are not used).
  • For Non-Bose Systems w/ Rear Factory Sub Amp: Connect the front channel speaker wires of this harness to the front speaker wire leads of your aftermarket head unit's wiring harness; then connect the rear RCA connectors of this harness to your aftermarket head unit's rear-channel preamp outputs (in this scenario, your aftermarket head unit must be equipped with at least two preamp outputs).
  • For Bose Systems: Connect all four RCA connectors (front & rear) of this harness to your aftermarket head unit's front & rear-channel preamp outputs (speaker wire leads are not used). Your aftermarket head unit must be equipped with two sets of preamp outputs (front & rear).

Our Product Research Team

At Crutchfield, you'll get detailed, accurate information that's hard to find elsewhere. That's because we have our own in-house Product Research team — they open the box, verify contents, check the owner's manual, and record dimensions, features and specs. We stay on top of new products and technologies to help people make informed choices.

Crux SWRAD-55 Wiring Interface Reviews

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Written By vinny110, albany,ny on Wednesday, August 20, 2014

Crutchfield Customer Review (What's this?)

good product

Pros: n/a

Cons: n/a

Just a brick now

Written By Swamprink, Wheatland, WI on Wednesday, July 09, 2014

Crutchfield Customer Review (What's this?)

I was required to purchase for half price just to get switched power to the factory amp. Lots of unneeded functionality - too big to fit behind radio - failed after less than a year.

Works All Except Rear Audio

Written By MDEEZE, Vancouver, WA on Friday, January 10, 2014

Crutchfield Customer Review (What's this?)

Works for connecting steering wheel controls - also controls rear sub but I do not have any sound coming out of my rear speakers. From what I have read on forums I will have to either rewire from the H/U or hook up an additional speaker amp, which is what I'll most likely do. 2007 Audi A3 2.0T

Pros: Works

Cons: Rear Speakers Don't Have Audio

Good Interface

Written By Atomic13MJB, Boston, MA on Friday, August 23, 2013

Crutchfield Customer Review (What's this?)

Good harness for doing what you need to get done. Had to call tech support for some clarification as the lines are not labeled that clear. Good thing I know a thing or two about wiring as the two remote wires they had labeled backwards - one for the amp, one for the antenna. Connect these in reverse and you'll have radio but when you switch to another input device you lose the amp and get nothing for sound.

Cons: Bad instructions for the connections. Had to figure out some of the wiring issues myself.

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