I thought I would write this up while it was fresh in my mind. I just replaced all four speakers and the head unit in my 1986 300 SDL. I wanted to share some of the issues I had and how I overcame them to get the system to a much better sound while maintaining the stock look. I hope y'all find this useful. Sorry, I do not have pictures as I did not have the camera with me when I did it. If you have questions feel free to respond/PM me and I will be happy to go into more depth.

Now for the disclaimer: PLEASE VERIFY EVERYTHING! I make no claims that I did this correctly nor that this will work on your car, this is just what I did. My radio has not exploded yet, and everything works in the car so hopefully I did this correctly. Feel free to correct/offer suggestions.

First the specifics:

I used the Sony MEX-BT5000, Boston Acoustics 6.5 (rear), and Boston Acoustics 4x6 (front). I bought all of these from Crutchfield, which was helpful when it came time to wire the harness for the head unit.


Head Unit

The old Becker came out easy. Here are the steps:

• Remove the ash tray from its holder.
• When the ash tray holder is fully extended look down and you will see two screws. Remove them and the whole assembly will come out.
• There are two silver tabs that are right below the radio. You will recognize them as they are roughly in the third portion of the support bar.
• Before you remove the radio, note that there is a security device at the back that will permanently disable the radio if you pull it out roughly. To make sure the radio still functions after you remove it, make sure you do not bust this tab when removing. You will know this tab when you see it; it hangs down and needs to be compressed to remove the radio.
• Now pull down on the tabs in front and slide the radio out (mind that security device on the back!)
• Remove the wires from the rear.
• The unit is out!
• For my radio, I needed to remove the clips; to do this you just move the rear of the clip up until it clears the tab holding it. The Sony was held in place by friction.

IPod Connector

I also put in the Ipod connector. This was not too bad, but you will need to crawl around under the dash.

1. To do this, I pulled apart the lower dash over the front passenger foot well. There are three screws along the top near the glove box and one behind the computer trim piece. The computer trim piece is next to the passenger’s right foot in front of the door. The cover just pulls off.
2. Be careful with this lower trim piece, there is a blower on the right that has an electrical connector. There is also a piece of plastic covering the underside of the dash that needs to come down as well.
3. Once these two pieces are out of the way, I ran the wires from the radio area to the foot well. I also ran the actual Ipod connector wire into the glove box.
4. I put the controller from Sony for the Ipod behind the trim pieces and reinstalled the trim.
5. I reinstalled the lower trim piece first and then put in the cover for the foot well. Be careful to get the venting hose lined up and the fan electrical connector re fastened before bolting it all down.


Wiring

The wiring for this thing is pretty simple as well. I bought my Head Unit from Crutchfield, so it came with a wiring harness that fit perfectly. The most important thing to note now is that if you do nothing but replace the head unit you will only use two speaker channels coming out of the head unit (this reduces the Amp output to half). The reason is that there is a built in Fader that controls all four speakers which takes the feed from head unit and distributes it. Here is how I bypassed it:

• You need to remove the little shelf/dish between the center console and the wooden gear shift cover. Mine simply pulled out.
• CAREFULLY remove the wooden trim plate over the gear shift cover. Mine had been broken at some point and the previous owner put in a wooden fix.
• Locate the bottom of the fader control (the little wheel that sits in the middle of the panel). Remove the wire connector from the fader.
• Cut off that connector. It is a little rectangular box that has 8 wires running out from it.
• Pull this wire bundle through the dash up to where the head unit will sit.
• Here is the fun part:
  • On my car the grounds for the speakers actually run to the head unit itself, it is the positive speaker wires to the rear that seem to need to come from the bundle that you just pulled through. It seemed to me that the power from the front channels was split to the back channel on the way through.
  • Going from memory here, but the red wire and the grey wire in that bundle are the ones you need (please check this! I could be wrong or it could be different for your car).
  • I ran the grounds for the speakers to the negative terminal on a 9 volt battery and then touched the wires from the bundle to the positive terminal until I heard the pop in the speaker.
  • The front speakers could be left alone, they seemed to only have power siphoned off from them.
• Other notes:
  • The power antenna is the blue wire.
  • There is a blue wire with a red stripe; this is the security wire and you will not use it.

__________________
86 300 SDL - Vesuvius

96 SL 500

Assumption is the mother of all screw ups.

Do not go gentle into that good night. Rage, rage against the dying of the light. - Dylan Thomas

All that is necessary for the triumph of evil is that good men do nothing - Edmund Burke