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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

14 Reviews | 1 question - 1 answer

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Our take on the Crux SWRAD-55 Wiring Interface

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.

You'll only be able to retain your steering wheel audio controls with a compatible car stereo made by Alpine, Blaupunkt, Clarion, JVC, Kenwood, Pioneer, or Sony. No other brands are currently compatible. Check the Details tab to see if steering wheel audio controls are retained in your vehicle.

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. 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

What's in the Box:

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

Crux SWRAD-55 Wiring Interface Reviews

Average Customer Review(s):

(14 Reviews)


Ax from Alameda, CA on 4/26/2017

2007 Audi S4
Crutchfield Customer Review (What's this?)

So many wires but eventually understood what was needed and what was not.

Pros: Had the right connections

Cons: Instructions could be a bit clearer

Wire Harness

Eric from Bozeman, MT on 4/18/2017

2002 Audi A6 Avant
Crutchfield Customer Review (What's this?)

Confusing directions and not very clear which parts were needed or extra. Worked in the end but lost some of my steering wheel controls. Plan on some online google time to figure it out.

Pros: Easily worked with existing harnesses once you figure out which ones to use

Cons: directions were not clear and confusing

Crux SWRAD-55 Wiring Interface

Anonymous from Lake In The Hills, IL on 4/10/2017

2003 Audi TT
Crutchfield Customer Review (What's this?)

This worked well but the instructions for the blue wire that turns on the amp is not clear. I had to watch online videos to figure it out.



Crux SWRAD-55 Wiring Interface

Tallis from Harvest, AL on 11/6/2016

2016 Subaru BRZ
Crutchfield Customer Review (What's this?)

Confusing, poor directions. Blocks out the K-Line for diagnostics!! You will not be able to computer diagnose the vehicle while this module is attached to the car!! I does function well though, cannot use the click wheels on my 2006 S4 though, can only scroll for volume and track forward/reverse.


Cons: Confusing, poor directions. Blocks out the K-Line for diagnostics!! You will not be able to computer diagnose the vehicle while this module is attached to the car!!

Crutchfield response on 11/17/2016 Once we saw this review, our Tech Support team reached out to Tallis to issue an apology and help him further. We'll either help him get the interface working the way it should, or help him return it for an exchange or refund.

Fairly Complex But Works

Jon from Guilford, CT on 6/28/2016

2005 Audi A4
Crutchfield Customer Review (What's this?)

It was fairly complex to hook it all up, mostly because it's made to fit many different car models/years. When connecting/splicing this harness to the head unit's harness, I strongly recommend temporarily twisting and taping the wires together and testing the head unit to ensure all the wires are connected where they're supposed to be, then make your final connections by soldering or crimping. The instructions could've been more clear on what some of the wires do. The kit comes with two identical SWC harnesses. I'm not sure why; you're only going to use one of them and throw the other one away. And even those harnesses are basically two separate harnesses taped together. You can cut the tape off and separate them entirely, which is what I did. One thing I don't really like about this harness is the rear speakers work, but they're at a significantly reduced volume from the front speakers. After doing some online checking, I found out this is a common problem when hooking up an aftermarket head unit and using the factory amp. You'd think a kit specifically for these Audis would have a solution for this built in, but no. I've heard of people correcting the problem with a line-out converter. Myself, I just adjusted the fader towards the rear to even it out and it sounds fine. The harness retains most of the SWC functionality. At first none of them were working, then I finally figured out they only work with the ignition on, and they don't work in the accessory position

Pros: Retains most (not all) of the steering wheel controls, overall easy integration into Audi's complex wiring.

Cons: Vague instructions, some redundant wires/harnesses, no fix for the reduced rear speaker output

Wiring kit for 2003 Audi A6

Mik from New Jersey on 12/25/2015

2002 Audi A6
Crutchfield Customer Review (What's this?)

The wiring kit made switching to the new radio a snap. All of the original functionality and speaker system worked perfectly from day one.



A jumbled mess of wires

BillH from Maryland on 9/8/2015

2003 Audi A6
Crutchfield Customer Review (What's this?)

Included with this package was a variety of harnesses which were included to cover the gamut of possible configurations of the Audi A6 (2003). The directions included as well as the directions from Crutchfield were very limited, and only because I have some experience with car stereo installations was I able to dope it out. There were also many, any wires which had to be spliced, I had hoped for a total or near total plug and play experience. All totaled, it took me two full days to install the radio (Although the back up camera took a considerable amount of that time). Other wires were poorly marked, for example the wire to the antenna booster was marked power antenna - those are two very different things!

Pros: It did work, and I was able to retain steering wheel controls.

Cons: Very poor directions, very very difficult to shove all of those wires into the dash. Crutchfield Tech support was knowledgeable, but condescending, insisting I received complete step by step instructions, even though they were only a few pages of instructions, and included instructions I was not interested in (Changing speakers for example).


Easy! from New York on 6/16/2015

Crutchfield Customer Review (What's this?)

The harness worked well. Support from Crutchfield and from Crux was wonderful!

Pros: Easy

Cons: None really

Great for 2004 Audi

jc from Oregon on 6/14/2015

2004 Audi A6 Avant
Crutchfield Customer Review (What's this?)

Makes it easy to connect to the factory harness and retain steering wheel controls.

Pros: Easy connections

Cons: A little bulky. Does require some organization and space planning.

Does what it should.

NDude from New York on 5/11/2015

2005 Audi A4
Crutchfield Customer Review (What's this?)

Worked fine with my 2005 Audi. I can use some of my steering controls. After contacting Crux they said they're working on adding more functionality. I do wish it was a programmable unit (like one of my crutchfield assistants said it was) so you could choose what to do with your steering controls. I also noticed an led is on always even when the car is off, I have some concerns about it draining my battery if I don't turn on the car regularly.

Pros: Interfaces my radio and my car correctly.

Cons: Could have more functionality or flexibility.


vinny110 from albany,ny on 8/20/2014

Crutchfield Customer Review (What's this?)

good product

Pros: n/a

Cons: n/a

Just a brick now

Swamprink from Wheatland, WI on 7/9/2014

2003 Audi A6
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

MDEEZE from Vancouver, WA on 1/10/2014

2007 Audi A3
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

Atomic13MJB from Boston, MA on 8/23/2013

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.


Hands-on research

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).

MakeModel Year

Steering Wheel Control Retention: The CRUX SWRAD-55 also features a steering wheel control output for Pioneer, Sony, Alpine, Clarion, Kenwood, JVC, and Blaupunkt 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).

  • 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.
  • The Phone/Voice button on the steering wheel controls is not retained in the 2006 AUDI A3 Hatchback with Concert Radio.

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 ColorFunction
BlackChassis Ground
Red+12 Volt Accessory
Yellow+12 Volt Constant
BlueAmp Turn-On
BluePower Antenna
WhiteLeft Front Speaker +
White/blackLeft Front Speaker -
GrayRight Front Speaker +
Gray/blackRight Front Speaker -
GreenLeft Rear Speaker +
Green/blackLeft Rear Speaker -
PurpleRight Rear Speaker +
Purple/blackRight Rear Speaker -
Purple/whiteVSS (vehicle speed sensor)
White RCALeft Front Speakers
Gray RCARight Front Speakers
Green RCALeft Rear Speakers
Purple RCARight 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 verify what’s in the box, 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.

Q & A

Customer Q&A

Crutchfield asked  
Why did you buy this?

Easy solution to retain factory connections and SWC.[ Matt  Jul 16, 2017 ]
included in the installation kit[ Troy  May 17, 2017 ]
without this kit you might as well just sing to yourself ! lol[ robert  Feb 18, 2017 ]
It was to ensure I would be able to utilize my steering wheel controls with my new radio.[ NICHOLAS TROY  Jan 20, 2017 ]
Bought this because it was listed as an accessory and I didn't want to get into the installation job only to find I didn't have the right components to complete it.[ JOHN A  May 18, 2016 ]
Required to retain steering wheel controls[ Phillip Nigel  Apr 03, 2016 ]

1 question already asked

This will depend largely on your vehicle. For details on installation please contact an Advisor by phone (1-800-324-9695) or online chat. They will be able to pull up your vehicle and give you the details on what you will need for an installation.[ Kenny  Mar 06, 2017 ]  Staff

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