What idiot decided to place the power softtop switch in the rear switch panel?
It's bad enough that you have to put your foot on the brake pedal to operate the power top--if you need to put the top up whilst still moving (slow moving traffic on an autobahn), you need one foot on the brake, the other on the accelerator to keep the speed up, then you have to try to locate the switch by feel.

The solution: swap the power top and ASC switches. After all, I can count the number of times I have switched ASC off on one finger!



Accessing the rear switch panel
Getting access to the rear switches is easy. Use fingernails or a very thin screwdriver to carefully lever out the switch blank, then reach inside and push out the alarm LED and the powertop switch.



Radio removal
The next step is to remove the radio to get access to the rear of the switches. Make sure you have the radio security code! There's a small flap at each side of the BMW radio that can be opened. If you then gently pull, the flap comes off. Use a 2mm allen key to undo the screws. Pull the radio out and disconnect the aerial plug at the right. Use a screwdrive to lever up the plastic assembly at the left rear, then pull the radio out.



Gear lever surround
Now remove the gear lever. The procedure is the same for manual or automatics. Just get hold of the stick and pull sharply upwards. Then remove the gear surround plastic by getting purchase with your fingers and pulling upwards.



Remove the gear surround and pull out the handbrake surround. Your car should now look a real mess like this



Accessing the front switch panel
Pop the ASC switch by putting your hand through the narrow radio opening and push from behind. Unless you have spindly wrists, a small child and some sweets come in handy here.



Planning the wiring
There are four wires going to the ASC switch (above) and five wires going to the powertop switch (below). The simplest route is to cut the wires, splice in extension wiring, moves the switches and join everything up again. But that's nine wires running from the front to the back of the console.



As two of the wires to each of the switches are the same--ground (brown) and illumination (grey with red stripe)--there's no need to swap these over, so that leaves only five wires to run. I chose to a white-sheathed three-core cable, and a black-sheathed two-core cable.

In the picture below you can see the four wires intended for the ASC switch. Two (ground/illumination) carry on to the powertop switch, the other two are connected to the black cable heading for the rear. Three wires coming from the rear in the white cable then connect to the powertop switch.



At the rear, two of the five powertop wires (ground/illumination) are connected to the ASC switch, the other three head for the front in the white cable. Two wires in the black cable come from the front.



The finished result
This was quite a long job, made more difficult by the cramped working conditions when cutting and stripping cables. But for me, it was one job that just had to be done! I just wished someone had thought of cockpit ergonomics before deciding to place the powertop switch in such a crazy place.





Tim Cullis, October 1999

Thanks to Kurt Schatz for his input on disassembly and Ron Stygar for wiring advice.

Some wiring pointers from Ron:
- In general, a solid red wire is hot at all times.
- A red wire with any color stripe is hot at all times after a fuse.
- In general, a solid green wire is hot in run and start.
- A green wire with any color stripe is hot in run and start after a fuse.
- In general, a solid violet wire is hot in accessory, run and start.
- A violet wire with any color stripe is hot in accessory, run and start after a fuse.
- In general, brown is ground.
- Gray with a red stripe is dimmed lighting.

However, the Z3 is the only car I've found, so far, to violate the 'in general' part.