BMW E46 3 Series Z8 Engine Start Button Install

Procedure:
Remove the dashboard panel and small glove box from around the driver’s pedals and below the steering column – four Philips screws to remove the driver’s glove box, one plastic push pin rivet, one Philips screw and the clutch pedal stop screw to remove the main panel. Remove the cover under and below the steering wheel/column. Two push pin rivets - push in the centre pins, they will fall loose, then pull downwards on the cover, it needs a bit of force to come free as there are plastic tabs holding the column surround together just behind the wheel. This will expose most of the area behind the lower driver’s dash, the ignition wiring loom and its switch terminals.

You will need to make two wiring ‘T’ offs from the larger 2.5mm green and 2.5mm blue/black wires either at the switch (circled in above picture), or I found it was easier to splice lower down under the steering column cover.
Use 2.5mm minimum cable here to make the two ‘T’ off cable joints; you can see I used red and black (circled in the picture below). Strip about 12-15mm off the PVC covering of the loom cores and twist the new 2.5mm cable around the bare cores. Ensure that you make a very good clean soldered connection with a medium to high powered soldering iron, as it is a high current circuit passing approx 40A to the starter solenoid. Use of Scotchlock connectors for these two joints is definitely not recommended. Plenty of tape to insulate these two important joints.

Make the lengths of the two new 2.5mm cables as short as possible, so the relay is situated close to this position. I fixed the relay and (optional) relay base to a strut just above and behind the driver’s glove-box with a couple of cable ties, see picture below.
Now to make up the relay connections. Crimp the new red wire (from off the original green wire) together with the fuse holder tail into one 6.3mm female lug, I also soldered this too as it makes for a very large conductor to crimp, tape over if necessary and push on to terminal 87 of the relay/base Crimp the other side of the fuse holder tail into a 6.3mm female lug, tape over if necessary and push on to terminal 86 of the relay/base. Fit a 2A or smaller fuse into the holder. Crimp the new black wire (from off the original blue/black wire) into a 6.3mm female lug, tape over if necessary and push on to terminal 30 of the relay/base. Crimp a longer length of the thinner 0.65 or 1.00mm cable (I used black) into a 6.3mm female lug, tape over if necessary and push on to terminal 85 of the relay/base. I ‘picked up’ and soldered an earth from a brown wire under here too, any size will suffice as it’s only earthing the relay coil so will be passing less than 1A.

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