I was looking to find a way to hard wire a power connection for my Valentine One radar detector. I had already read through Richard Carlson’s “cutting the cord” article so I felt familiar with the task at hand. This was a great resource, and I recommend you read it first because he has excellent instructions at how to get the plastic panels off, as well as some good warnings. However I wanted the power source to drop from top of the A-Frame rather than up through the dash. The MZ3 has enough room above the rear view for the V1 to slide into (click on the picture for a larger view).
First, a quick lesson about BMW wiring. Turns out that everything is color coded, which makes finding a power source a little easier. Red wires are unswitched power sources (on all the time). Purple (with white stripe) wires are switched power sources (on when the car is on). Brown wires are ground. Depending on which type of power source you want you can choose which wiring harness to use.
The information below is specific for the M roadster’s, it has come to my attention that the wiring on the 1.9 and 2.8 roadsters is different. The color coding is the same but wiring harness locations are different. If you own a 1.9 or 2.8 you’ll want to focus on the area behind your stereo, tapping into its switched (purple and white wire) power source.
A couple M owners spoke with me after using the information below. The first spent about 45 minutes to an hour and commented that everything was straight forward. Thought he could do the job again in less time. The second M owner that spoke to me said the wiring was straight forward but the black plastic trim pieces (under the dash) gave him a lot of trouble. I think he summed it up best by saying “I did it!, but you couldn’t pay me $100 to do it again”.
If you want an unswitched power source there is an unused power connector down by the drivers feet (click on the picture for a larger view). This connector has a positive and a negative unswitched power source. It is in a convenient location just below the speaker. To gain access to this area you will need to remove the lower kick panel and the panels covering the underside of the dash.
Problem was, I was in a picky mood and wanted a switched power source. Under the dash you can locate this connector (BMW calls it X223 – the connector is next to the 40amp fuse strapped to the MAIN wiring harness), it had 5 wires in the connector (click on the picture for a larger view). I know it’s hard to distinguish colors in this picture because of the flash but the left most wire is ground (brown) and the one next to it is switched power (purple with white stripe). In this picture the middle wire is pulled out of the connector (speed sensitive volume connection – another project).
The Valentine One radar detector came with a wiring kit. The black box in this picture is part of that wiring kit. Since this box wasn’t a BMW part the color scheme doesn’t quite match but the red wire out of the box was connected to the purple power source. The black wire was connected to a good grounding point (see the bolt and brown wires next to the speaker)
Once the connection was made all that was left was getting the wire to the radar detector. There was just enough of a gap on the side of the dash to slide a wire back to the corner (like using dental floss). Now the wire had made it to the top of the dash the A-Frame cover just pulls off and you can run the wire under the plastic cover. Along the top you don’t even need to pull off the plastic cover. There is enough of a gap to push the wire in where the plastic piece meets the window.
You should actually work backwards so you have just enough wire sticking out where the radar detector mounts, and bundle up any slack down below where it is easier to hide it.
If you are anywhere near Dallas and would like a trained BMW expert to do work like this for you, I can highly recommend Larry Nissen. Larry did the work on my car and took the time to explain everything for me.