Hello all,
So as I am becoming "friends" with my new to me 2005 one more thing to fix was the auto headlight function. Not to be confused with auto mirror dim. My symptoms were the lights in auto were always on making seeing the dash and buttons / radio hard to see in the daylight since they dim those functions. In the lights off position and running the car would yell at me that the "lights are off" and it was getting annoying. all other functions worked specifically the auto dim in the mirror. Different sensor. On the newer XKs there are more sensors in the mirror and many posts only address earlier models. I found several variances after getting a salvage mirror assembly home only to be totally different. Here is what I found. For starters this thread was very informative but strayed between functions, wipers, auto dim and until I got my apart was slightly confusing being new to XK8.https://www.jaguarforums.com/forum/x...nction-192402/
So here was my journey

My windshield. The picture is from the roof looking down at the windscreen. The Green arrow is the rain sensor, the red is the actual photo diode (my words) that senses the light and completes the circuit. It is actually soldered to a mini circuit board in the mirror assembly. The yellow is a plastic cover that hold the circuit board in place sandwiched between the glass and the mirror assembly.



Here is the mirror assembly out and the blue lines are where the sandwich cover will install before installing on the glass mount. The Red arrows are to the photo sensor itself and the solder joint that failed on my mirror. Re-soldered and it works.


Here are the removal instructions of the cover and mirror




Something else to note. 2 Part numbers show up for my 2005 Jag C2P1823 says it fits all model 2003 to 2006 even when I punch in my cars info. Sure it fits but it's not what is in my car. C2N2931 shows up as 2005 and 2006 only. This is what I have and you do to if you have the triangle dark on your windscreen like in the earlier pics. Here are diagrams of the parts. Wrong first Correct second.



Hope this helps guys, after a good fight it works. Also worth noting the inside sensor circuit board was loose in the assembly so a little silicon helped to keep it in place.

Cheers, Mike