Switch
This is the interesting part. I needed to come up with something that looked, felt and behaved OEM, for both the PDC and AEs. Thanks to Z4 Beemer and Oakandacorns who got me looking at the main console switch panel, I dismissed it. Here I would need:
1. The buttons had to look the same as the existing one - size, shape and backlighting with OEM style labels.
2. Buttons that would have a tactile push, on and off - rather than a locking switch
3. They would need to reset if the ignition was switched off and on again - like the DSC, fog lights, etc.
Making the buttons.
I dismantled the switch panel, taking out the buttons and holder, splitting them down to their component parts. Set these in a silicone rubber mould. Fill the mould with liquid plastic, leave to set and then remove.
I had to do this a few times to get something I could work with. This is still relatively new to me.
I cut out the buttons and sprayed with an acrylic model pain - had to mix black and white to get the right colour. Again, took me a few goes to get a match. I then used a small point screwdriver and a wash as a guide to etch out something resembling the BMW light symbols with an AE add-on and a PDC symbol.
Behind the BMW switches are small circuit boards, obviously I needed to make my own. I cut a strip of circuit board to size and used a small momentary (only makes a circuit when pushed) tactile switch for the button (not as much travel as the BMW ones
). I added the back light LED - I took this off some moody orange LED indicator light I bought off eBay, that never worked, with a resistor attached. There is also a second LED which is the on / off indicator. This was red for the AEs and Green for the PDC in the end.
From my lab / living room tests, I found that the tactile switch didn't work consistently - either many times in sequence or not at all. For some reason I decided to fit resistor, this solved the issue. This is all new to me - I've never made a circuit board before or even soldered for that matter.
I was very careful to colour code all of the wires coming off the back of the switch to go into the connectors.
I used two connectors. The first was for the back light LEDs, I connected these to the supply for the small LED by the cigar socket in the ash tray. This mesa that the back lights dim and brighten with the rest of the dash, again info from the WDS.
The second connector handled the operating LEDs and two wires for each of the switches.
Front of the switch with the new buttons in situ:
To re-fit the front of the switch I needed to drill some holes. BMW, as they often do, kindly marked out the holes for the heated seat buttons, but not the one in-between it and the run flat indicator. I used masking tape to work out the position of the holes and then set about making a mess. Thankfully it paid off…
The front of my modified switch panel.
The switch was then fitted to the back of the console. Wires obviously tidied. Not sure how well it can be seen, but I needed to cut a hole into the back of the switch so it can pass over the connectors if I ever need to.
That covers the look and feel of the switches. Next, the operation. I needed the switches to operate on single pushes, on and off. This took some research, but I found Flip-Flop relays. This uses a push button to operate the relay between open and closed - the tactile switches. Here are the Flip-Flops for the PDC and AEs in there cases - which I had to cut down and weld to fit under the dash.
The Flip-Flop has two power inputs, one for the relay Normally Open (ie you need to push the button to make the connect and turn on the power) and the second Normally Closed (the power is on by default).
For the PDC I connected the Normally Open power supply, the button push tuning on the PDC.
For the AEs rather than wiring the power supply into either Normally Open or Normally Closed I sent it to a switch. One connection went to Normally Open, the second to Normally Closed. This allows me to choose which state I want the lights in. At the moment they are new and novel so I was them on all the time, if later I want them off by default I simply flick the switch, located to the left of the base of the steering column.
For both relays I removed the LED indicator with a soldering iron, replaced with cables and wired these through to the corresponding switch.
Also, the relay resets when the power is cut, so turning off the ignition returns the switch to its original state.
Next job was to wire the lot into the car. Started as a mess, loomed and then hidden.
could you fabricate a supercharger for me?! 
brilliant job 
Tough audience.
