Just bought a 2012 135i M sport convertible last month and love it, EXCEPT for the horrible rear and rear panel vision with the top up. The "sonar" type image on the Nav screen and the sound warnings are good for parking, but not for rear vision. There have been several solutions to this, the best one, by zx10guy does a lot and is completely integrated into the idrive screen but is about $700 and you have to tear the whole dash apart and figure out where to squeeze the units in. There are also other DIY discussions about this and they vary from wireless systems that use your iPhone as the screen to other ones that have to be hot wired in front or use a cigar lighter socket for power.
After some research and reading what others have attempted I came up with my own solution that is now working like a charm and is inexpensive. Installing it was fairly difficult, mainly getting the cable through the trunk tube and then getting it up to the inside area from the trunk, but I figured it out and this will make it easy for others without having to guess like I did. Also, there is a weird problem that others have run into where there is a lot of screen static and then a black, dead image. Using a trip relay can solve that problem but is also overly complicated and not necessary. All that is needed is a simple, inexpensive, rectifier to get rid of the AC signal riding on the 12-14v DC on most newer German makes.
For those of you just wanting to be able to clearly see what's behind you when backing out of a parking space with the top up and only spend $60 and maybe 4 hours work, here is my solution:
The system I chose is made by
Boscam or by
Audiovox and appear to be identical and the same price at $50 with shipping on Amazon. They each have the advantage of having good resolution and night vision and viewing angle and only requiring one power hookup at the rear backup taillight wires which also trip them on when in the reverse mode. But like many other units, they won't work on German cars unless you put a rectifier between them and the back up wire power source. I found this
Dasaita rectifier does the trick for only $10 with shipping on Amazon. Here is the hookup for my 2012 (check to be sure your wiring to the back up light is the same):
Here is the finished install which only comes on, with no delay, when I go into reverse:
First you have to remove the panel on the trunk lid held on by 8 connectors. The camera is attached behind the license plate. It comes with a centered hole, but I didn't want it centered over the screw cover, so I drilled another hole to the right of it. I then drilled a hole in the right license plate light plastic housing and fed the cable up through that hole. Here's a photo and how it ends up looking very inconspicuous and hidden:
With the cable inside the trunk lid it is fished down to the right where the flexible tube joins the body. (the green line in the photo) This is the fairly hard part, getting the cable through the tube which is already full of wires.
Undo both ends of the tube and using KY jelly fish a 14 gauge electrical wire through it. Then using electrical tape, attach the cable to the end of the fish wire and lubing it up well, pull it through the tube. You will have to try to get the tube straight and do a lot of pulling back and forth, but it will eventually go though. (note: do not use dish soap, etc. as they are caustic and can damage the wires, KY jelly is safe on rubber and plastics) When you get it through the tube you are going to use the same fish wire technique to get the cable down into the trunk area where you have removed an access panel on the right. (see the photo). Lub up the ends of the tube and reinstall the tube by working them back into the sheet metal on the lid and the body and be sure they are well seated and secured. You can then put the trunk lid panel back on, concealing the wires or wait till later. Here's a photo:
Now you plug the camera cable into the marker switch, connect the red + and black - wires to the rectifier and connect the rectifier input wires to the tail light back up wires. I soldered the connections between the marker switch and the rectifier and wrapped them in electrical tape. For my E88 the rectifier wires attach to the tail light positive black/purple and the negative attaches to the brown. I used wire taps so as not to have to cut the tail light wires. Wrap up excess power wires with the marker switch and mount it behind the removable panel with some bubble wrap so they don't rattle.
Next you need to run the long cable from the marker switch up into the cabin and to the screen in the front. I spent a lot of time trying to figure out how to get the cable into the cabin and finally came up with this solution. Put the convertible top half way down as shown in this photo.
You will see that there is access up into the top storage from the trunk. Put the top back up, then from the trunk, using your fish wire again, feed it into that upper top down area. Close the trunk and put the top half way down again. Using you fish wire pull the cable up into the top storage area. Lay it along the existing wire run as shown in the photo and secure with ties. Then feed it through the hole in the sheet metal. You are going to feed the cable down into the cabin after removing the back seat cushion. Here's a photo of the part way down top with the wire feed path.. be sure it isn't going to come in contact with any moving parts.
The back seat cushion has two front center clips that remove fairly easily when you pull up on the seat, There are two other bigger ones on either side that you really have to pull up hard on the seat to release, but then you can remove the seat completely.
When you fish the cable down to the seat you can then run it over to the center area and fish it over to the center drive train column where you can easily tuck it under the plastic panels covering the carpet and up to the front of the dash, then over to the cubby hole in front of the shift. It will be completely invisible, except for maybe a very small area in front of the seat over to the rear of the center console. Put the back seat bottom back in.. it's difficult because you have to get the seat belt retainers into the two holes in the seat bottom. I ended up pushing one up into the hole, then attaching it to the seat belt, then the other, then I pushed the seat back in place and snapped in down onto the four front retainers.
OK, at this point, you can plug the long cable you ran into the screen cable and put the screen in the cubby hole using the supplied adjustable base like this:
If you do it this way, it will sit up higher and will be more permanently mounted. I wanted it to sit lower down and be easy to remove, but secure, so I ended up fiddling around cutting some packing foam, the rubbery kind that cuts cleanly and doesn't make a mess and I then spray painted it flat black. Here are the rough dimensions and what it ended up looking like. The screen pushes into place wedged between the dash and the consol while the foam under it pushes up and keeps it in place and it is very secure, but can be removed easily and is unobtrusive.
Hope some others here find this useful and feel less intimidated to take on a rear camera project and with out spending a lot.