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Crux SWRBM-57 Wiring Interface

Connect a new car stereo and retain the factory amp and steering wheel audio controls in select 1999-up BMW and Mercedes-Benz vehicles

Item #: 249SWRBM57

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16 Reviews | 1 question - 1 answer

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You'll only be able to retain your steering wheel audio controls with a compatible car stereo made by Alpine, Blaupunkt, Clarion, Jensen, 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 SWRBM-57 interface ensures that you can keep the steering wheel audio controls and the factory analog amplifier in your vehicle when you replace the factory radio. Connect this interface to the wires on your new stereo's wiring harness, and you've covered the power, ground, and factory speaker connections for your new stereo.

The SWRBM-57 interface also offers the parking brake, reverse, and Vehicle Speed Sensor (V.S.S.) outputs that you'll need if you're installing a navigation receiver. Note: This adapter will not work with the digital amp used in some 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 1999-2013 BMW, Porsche, Mercedes-Benz, and Smart models
  • retain your steering wheel audio controls and use of non-digital factory amplifier
  • provides connections for Vehicle Speed Sensor (V.S.S.), reverse gear, and illumination for installing navigation receivers
  • warranty: 1 year
  • Our 60-day money-back guarantee

Crux SWRBM-57 Wiring Interface Reviews

Average Customer Review:

16 Reviews

Perfect fit

Written by: Batfan from Georgia on October 25, 2015

2004 Mercedes-Benz C-Class
Crutchfield Customer Review (What's this?)

made life super easy when removing the stock HU and installing a Kenwood!!!



Straight forward install

Written by: Q-man from California on February 27, 2015

2005 Mercedes-Benz C-Class
Crutchfield Customer Review (What's this?)

Installed in a 2005 Mercedes Benz C240-Base sedan. Previously I had purchased the Axxess ASWC-1 Controller and had nothing but problems. Constant issues with the Air bag warning and random door unlocks while parked until it stopped working all together. So obviously I was not going to order another one. This unit was a much better install as the harness coupled perfectly with the factory harness. No extra splicing needed. Worked from the start and also gave me the option for illumination control.

Pros: No extra splicing needed. Connects to factory harness. Works.

Cons: Only volume and station/track controls available.

Makes life so much easier.

Written by: Jim R. from Farmington, NM on February 23, 2015

2007 Mercedes-Benz C-Class
Crutchfield Customer Review (What's this?)

Made the radio installation in my Mercedes very easy (at least the wiring part). Everything worked perfectly the first time.




Written by: Jake from Florida on December 8, 2014

2004 Mercedes-Benz C-Class
Crutchfield Customer Review (What's this?)

Take your time and read the radio manual, these directions and it will hook up perfect first try. At least for my C230K it did.



Crux SWRBM-57 Wiring Interface

Written by: Tom from Ohio on November 21, 2014

2007 Mercedes-Benz C-Class
Crutchfield Customer Review (What's this?)

Crux SWRBM-57 Wiring Interface. Used in my 2007 Mercedes Benz C280. Work flawlessly to connect my stereo to my steering wheel controls. Allows me to control basic all functions of the stereo from volume to changing stations to changing songs on my iPod. Very happy, reasonable price. Easy to install.

Pros: Easy to install

Cons: None.

Crux Installation

Written by: Jay McC from Las Vegas, NV on November 21, 2014

2005 Mercedes-Benz C-Class
Crutchfield Customer Review (What's this?)

I received the Crux and Pioneer double din from Crutchfield nervous to install the system myself. I Consider myself to be very handy, but I have never put in a car audio system myself. First off, the Crux had very good instructions, but I did have a couple of questions I needed to discuss with a Crutchfield technical advisor. These guys are amazing! I liked the simplicity of the advisers knowing who I was and what items I ordered because of caller ID. The Crux and the Pioneer went in without any issues

Pros: Easy to install, works as expected

Cons: I was hoping the steering wheel phone button, would work with Siri. That's my only complaint

Works great

Written by: ToddP from Ellicott City, MD on October 7, 2014

Crutchfield Customer Review (What's this?)

This is the best and most cost effective method to get a new radio into my 2000 CLK and keep the steering wheel controls.

Pros: - Easy to install - Volume and skip (change preset) work fine - Fair price

Cons: - Phone answer/hang up buttons don't wok from the steering wheel controls


Written by: ET from Tacoma on October 2, 2014

2002 Mercedes-Benz C-Class
Crutchfield Customer Review (What's this?)

This product is incredible, did exactly as advertised. No fuss no hassle. I replaced my 2002 C230K stereo in a matter of minutes using this adapter. No programming necessary for my steering wheel functions to work perfectly

Pros: ease of installation, only one adapter needed as this does it all.

Cons: It didn't wiring itself up while I watched.

Pleasantly Surprised!

Written by: Xeeker from Bentonville, AR on May 5, 2014

Crutchfield Customer Review (What's this?)

I was pleasantly surprised when most of my steering wheel controls worked! Not only did the volume buttons and the track changer work, but the air control (BMW 3-series) worked, too! As a matter of fact, the only button that didn't work was the phone button (which I expected since I wasn't using the built-in phone any longer).

Overall, very impressed.

Pros: Easy to use/install Lots of functionality. Volume Controls Track Changing Controls Function Changing Controls (Radio -> Aux -> CD, etc.) Air Circulation Control (BMW 3-Series)

Cons: None!

Crux SWRBM-Factory Integration Adapter

Written by: Marv from Pebble Beach, Ca on May 4, 2014

Crutchfield Customer Review (What's this?)

Will only control the volume, no scan or phone functions, Your customer service rep. says it will have to replaced.



Crux SWRBM-57 Wiring Interface

Written by: Anonymous from San Francisco Bay Area on May 3, 2014

Crutchfield Customer Review (What's this?)

Installed in 2008 BMW 3 series. If it worked it would have been great but the 12v constant connection from the adapter goes away after roughly 2 hours, causing my stereo to reset. I read that BMW's go into a deep sleep mode after a few hours and if you want 12v constant, you have to either run a connection to the battery or tap the fuse box.

Pros: Easy to wire up.

Cons: 12v constant went away after 2 hours causing stereo to reset.

Flawless comtril

Written by: Irez from San Antonio, TX on February 6, 2014

2006 Mercedes-Benz C-Class
Crutchfield Customer Review (What's this?)

Easy snap and play for my Pioneer Deck to my C280 Mercedes.

Pros: Steering wheel control works great



Written by: Allen from Cumming,Ga on January 20, 2014

2007 BMW 3 Series
Crutchfield Customer Review (What's this?)

Great product, easy install!

Pros: Very easy to install and works great!

Cons: N/A

Great Harness

Written by: Jesse from Birmingham, AL on January 15, 2014

Crutchfield Customer Review (What's this?)

Was very easy to use and set up. The unit programmed itself and i was able to control my radio volume, change tracks, and change the radio source with no issues. The phone button and voice commands do not work but i think that is because my car didn't have those features anyway. I haven't looked into it much yet. 2006 BMW 325i



Works perfect

Written by: Denny from Fort Wayne, IN on November 22, 2013

2002 Mercedes-Benz C-Class
Crutchfield Customer Review (What's this?)

Used this on a 2003 c230 and it worked without a problem. Still have radio function in the wheel, antenna works great.

Pros: Ease of use, no wire cutting on original harness

Cons: Antenna wire could be defined a little better

Cool product

Written by: Bill M from Torrington on November 21, 2013

2006 BMW 3 Series
Crutchfield Customer Review (What's this?)

Wire the deck and plug it in !!! No programming and it keeps most of your steering wheel controls .



Hands-on research

What's in the box?

Download owner's manual

  • Radio replacement interface module (for BMW/Mercedes)
  • 2 Wiring harnesses
  • 2 SWC harnesses
  • Installation Instructions

Product Research


Audi Radio Replacement Interface: The CRUX SWRBM-57 is a radio replacement interface for select BMW and  Mercedes vehicles. It facilitates the integration of an aftermarket radio to enable retention of factory features when replacing a factory installed radio. This interface is also pre-programmed for retention of steering wheel controls.

Compatibility: The CRUX SWRBM-57 is supported by the following BMW and Mercedes vehicles; with non-amplified or amplified factory audio systems (including Bose). Not compatible with vehicle's featuring fiber-optic digital amplifiers.

Make Model  Year Harness
BMW 1 Series (E81/82/87/88) 2007-2013 Quadlock
3 Series (E90/91/92) 2005-2012 Quadlock
Mercedes A-Class (W169)  Audio 5 2004-2010 ISO
Quadlock 2004-2010 Quadlock
B-Class (W245) Audio 5 2004-2010 ISO
Quadlock 2004-2010 Quadlock
C-Class W203 2000-2003 ISO
W203 2000-2006 Quadlock
W204 2007-2012 Quadlock
CLK-Class (W208) 1999-2002 ISO
E-Class W210 1999-2000 ISO
W212 2009-2012 Quadlock
M-Class (W164) 2005-2011 Quadlock
R-Class (W251) 2006-2011 Quadlock
SL-Class (R230) 2001-2004 ISO
Note: Two vehicle harnesses (Quadlock or ISO) are included with the interface; you will only use one of these harnesses based on your type of vehicle. 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 SWRBM-57 also features a steering wheel control output for Pioneer, Sony, Jensen, 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 SWRBM-57 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 SWRBM-57 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 SWRBM-57 provides an amplifier turn-on lead for your vehicle's factory analog amplifiers (if equipped). This adapter is not compatible with vehicles that feature fiber-optic, digital amplifiers.

Wiring Harness: The SWRBM-57 includes two wiring harnesses; there is a 2-connector factory harness (16-/10-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 SWRBM-57 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.

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

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.

Customer Q&A

1 question already asked

This will depend largely on your vehicle. For details on installation please contact an Advisor by phone 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, as well as answer your additional questions. [ Jeff  Jan 10, 2014 ]  Staff

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