Signal to Noise	Mercedes-Benz Specs	Coupes	Convertibles	Sedans	Miscellanea

Before beginning, I'd like to address a few rumors. Many people claim the head unit (radio) on a modern Mercedes-Benz cannot be replaced without considerable effort. Web gossip includes tales of dashboard error messages, a complete rewire is required, the entire audio system is linked by fiber optic cable, Bose amps and speakers are incompatible with aftermarket devices, the multifunction steering wheel controls will be lost, and that other systems may be negatively impacted if "the system" does see the factory radio.

In the installation outlined here

• There are no error messages.
• The existing factory wiring harness was used without cutting any Mercedes-Benz wires.
• There is one fiber optic cable. That cable runs to the obsolete CD changer (audio CD technology is over 30 years old, it has been superseded by SSD devices).
• The original equipment Bose amps and speakers were retained. They both sound and work as Bose Corporation had intended.
• The multifunction steering wheel controls work
• No other systems were impacted.

A different manufacturers amps and speakers could have been used. In that scenario, additional wiring would have been required. However, no more so than if an entirely new system were installed in any other car. The steering wheel control functions are independant of the amps, and would work in either situation.

After deciding which features were desired, the next things needed were the parts. The parts were purchased from Crutchfield, and the following part numbers are from their catalog.

Note: The SWI Jack only works with JVC, Alpine, Clarion, and Kenwood head units. Different PAC converters are required for other head unit manufactures.

The following is a schematic of the finished product.

Looking at the head unit, starting with the upper left connection, and going clockwise

• The Alpine head unit has a female Motorola antenna jack. Mercedes-Benz uses a European male plug. An antenna adapter was used to complete the connection.
• Next is the remote control port for the steering wheel controls. The PAC SWI Jack plugs into the remote control port on the head unit. The PAC SWI-CAN2 plugs into the PAC SWI Jack. The CANBUS wiring harness plugs into the PAC SWI-CAN2. The Steering wheel controls send a signal through the CANBUS wiring harness.
• The remaining connections all go to the PAC OEM2. The PAC OEM2 converter box is the middleman between the head unit and the wiring harness adapter. To retain the Bose sound quality, a PAC OEM2 was used. Bose uses a balanced, differential signal interconnection. Most aftermarket audio systems use an unbalanced connection. The PAC converter box reads the unbalanced input and produces balanced output. The ground, constant power, switched power, speakers, and illumination lead are attached to the head unit on one side of the OEM2, and the wiring harness adapter on the other side.

Before touching the car, some pre-assembly was completed. For those who have previously installed a car radio, this is all straightforward. A crimping tool and blade connectors were used to attach the Alpine head unit wiring

to the input side of the PAC OEM2.

The output side of the PAC OEM2 is then connected to the wiring harness adapter.

After making those connections, the wiring harness adapter is ready to be plugged into the Mercedes-Benz wiring harness. The PAC SWI Jack and SWI-CAN2 can now be set up.

The jack for the SWI Jack plugs into the head unit's remote control port.

PAC supplies a wiring harness that connects the PAC SWI Jack and SWI-CAN2.

The wiring harness from the SWI-CAN should be connected. The SWI-CAN instructions specify wire colors for the ground, switched power, and constant power. The wires for the CANBUS connection are very important. On the unit that was used in this installation -

• White/Red is CANBUS positive
• White/Black is CANBUS negative

Radio Shack supplied blade connectors that matched the CANBUS slots. The connectors were attached to the SWI-CAN wires. This allowed the individual positive and negative CANBUS SWI-CAN wires to plug into the Mercedes-Benz wiring harness.

The SWI-CAN documents will have a connection schematic with 13 different CANBUS plugs. If you are working with a CANBUS plug that differs from the one on this page, one on the schematic will probably match.

The PAC SWI-CAN instructions made this a simple installation. Crutchfield also supplied their own vehicle-specific CANBUS installation docs.

At this point, work on the car can begin.

Before removing the factory head unit, the storage compartment below the radio was slipped out. The radio removal tools were then inserted until they locked into place. At that point, the radio removal tools were used to pull the radio out of its slot.

There is plenty of room to slip the radio out, and then unplug the cables.

The rear of the radio that was replaced is shown below. This radio has five ports.

• Port 1 is the CANBUS connection. It's used for the steering wheel controls.
• Port 2 is used for the power and speakers.
• Port 3 is used for speakers.
• Port 4 is a fiber optic port for the CD changer.
• Port 5 is for the antenna.

  

  The new head unit simply replaces the old one. The new sleeve is installed. The USB cable is attached to the USB port on the new head unit. The USB cable was then run to a convenient location. On this particular head unit, the USB connection was used to read iPods, iPhones, and solid state drives. The OEM2, SWI-CAN, and SWI Jack are stacked in the spot below and behind the head unit.

  • The vehicle cables that used to plug into ports 2 and 3 were plugged into the wiring harness adapter. The cable that was plugged into port 2, was plugged into the top half of the wiring harness adapter. The cbale that was plugged into port 3 was plugged into the lower half of the wiring harness adapter.
  • The individual positive and negative SWI-CAN CANBUS wires to plug into the positive and negative CANBUS slots on Mercedes-Benz wiring harness.
    
  • The antenna plugs into the Motorola-to-European adapter.
  • The fiber cable for the CD changer is left unplugged - with SSD, who needs CD's?

  The only things remaining are some minor programming for the steering wheel controls. Instructions are included with both the SWI Jack and the SWI-CAN. The programming instructions are very simple; setting two rotary dials, pushing some buttons, and turning the ignition off and on.

  The SWI programming instructions have been intentionally omitted from this page because they may differ from one SWI kit to another, and/or PAC may change the instructions.

  

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  I have no way of determining anyone's skill level. Some people may glance at this, buy some parts, and have an upgraded car stereo in very short order. Others may study this intently, plug 12V positive into the negative port of the CANBUS plug and find themselves with "issues". Therefore, everything listed here is for entertainment value only. I highly recommend the services of a skilled technician be used for any modifications. I also do not guarantee the accuracy of these documents and under no circumstances shall the product manufacturers, distributors, website owner, or those affiliated with this website be held liable for any damages sustained while trying to replicate anything discussed on this site.