1) First (I knew this but apparently not common knowledge) the electrical portion does not need any programming to work when replaced. Nor does the mechanical keyed portion. Nor does the Antenna ring that reads the key chip!
2) The unit is mostly mechanical with hidden wires from metal contacts (like an old fashioned distributor point set). These must have either metal or wires hidden within the plastic body running to the out/inlet pins for the plug.
From a fading memory, I thought I had had this changed out several years ago. Looking through my receipts I found a dealer workshop repair receipt for a replacement. Reason? Random dash warning lights and engine running rough! That sounded familiar!!
3) Abscate reminded me that the handbooks used to warn you to leave the ignition key in and turned to POS II when re-connecting the battery. I never have done this as I used to find it caused a large spark when connecting the ground lead. Now, that may be because I have an aftermarket Viper remote starter and immobiliser fitted. I think this is also the reason for my larger battery current draw with the ignition off. (around 0.45-0.65mA).
4) The part number in the title is the ONLY part number. You may see other numbers quoted but there was one older part number pre P2 which was consolidated to the new number in title.
5) Any other numbers quoted are the number molded into the black base of the switch which is a component part number and not that of the whole switch.
The root cause I believe for the failure (other than my stupidity!
I connected up the battery and when I started the car there were loads of warning light on the dash when it was running and the engine ran rough. Looping back to 3) above may explain the need for this. Not being an electrical genius (well genius of any sort
Abscate has offered to to an autopsy on the article and I may still send it to him to complete this process. I was curious so decided to open the unit and see if the insides were baked and black.
I opened it and found no obvious or non-obvious signs of charred remains. In fact the unit looks mostly well built if mechanically old fashioned. Mine showed no signs of wear or burning on the electrical contact pads after 5000 miles of use.
My conclusion is that the hidden wiring must have fused or melted internally within the body of the unit and I don't plan to take this apart further. I have attached pictures of the dis-assembled unit below:
The spring in the cover is what returns the key from POS III to POS II after starting the car.
The ivory colored plastic pieces are pushed down by the cover above then in turn as you rotate the key in the barrel. That closes the contacts at each position.
On the top side of the cam cover if you look carefully you can see a slight inward movement of the outer ring. In that a small protrusion in the cover sits to control the amount the electrical switch can move.
Not sure if this helps at all. I however found it interesting to understand how it works.
Neil.






