This is an excellent mod that it can also be practical!
I had it wired to the courtesy light as well, however i later installed an illuminated ignition ring, so i piggy-backed from that wire. In that kit, they give you connectors so you don't have to alter any of the original wires.
I still cannot comment on the -AA or -AB issue. Apparently there is -AC as well. I only tested with an -AB sensor, and i still haven't found the pins needed... :S
Once you activate everything through ELM, you can easily check which one works. Just plug it in (with the engine on ON), and before you position it on the windscreen, cover it to simulate darkness. If the headlights come on, that means that the sensor will be OK to use.
The part of the sensor that attaches to the windscreen is interchangeable. You can easily open the housing using a coin or your keys. Just insert them to the side gaps and twist. If the -AA doesn't work, just put the cover with the silicone on the -AB.
I don't see why the -AA won't work. I compared the electronic parts inside both of them and they look identical. There are different revisions however, which makes me think that they might have different sensitivity levels, or configurations.
I haven't glued the metal plate yet. In fact, i haven't finished the whole mod yet. I have tested that it works, but i still haven't been able to source the correct pins to connect the switch with the fusebox.
If anyone can show me the correct type of pins, it would be great. I know which ones i need, but i cannot find an exact match on eBay or RS-online.
Regarding the mirror mount, i think the old part will not fit easily, so i would create something from scratch rather than use the existing mirror.
Kurt, if i were you, i would avoid gluing the mirror. If you need to remove it for whichever reason, you will have huge issues and you might even break the windscreen.
If the cutting did not go well and you cannot alter it to fit, i would recommend to craft something that will slide into position. You can then cut away the remaining part of the mirror base and glue that to the crafted part.
Also, you do need something to hold the sensor in place. Captain Haddock has posted an image of his sensor where you can see how it attaches to the windscreen.
Unless the sensor is attached to the windscreen firmly and there is silicone between the two, you will never get optimal results.
Having only basic knowledge of electrical systems, i decided to use a multimeter at the cable leaving the switch when the engine is "ON" and the switch set to "Auto" hoping that i would at least see if there is any current running through.
Surprisingly i couldn't find that cable on the loom, so i now need to try and locate its position on the fuse box. If that is blank, I can then try and install a cable from another loom i have hanging around and hope that it will work.
If someone could tell me which connector on the fusebox is the one needed, that would be great.
I believe that the connector is number 5 on C103 which is the long blue one on the left. I did install a wire running from that to position 52 on the switch, but nothing happened. Do i need a second wire?
Kurt, to remove your current mirror, you need to get a flat screwdriver and push the locking part up (away from the windcreen).
The wire and connector going to the switch are the same for LHD and RHD. I was reluctant in buying one because they are expensive and i would have to resell it, but i finally decided to give it a shot. I'll collect it tomorrow and test.
Prior to ordering the switch, i disassembled my current switch and everything seemed to be in order, so i doubt a new switch will make any difference. I'll report back tomorrow.