Was going through some bins of parts off the ‘96 XJ12 today and found the Donnelly electrochromic rear view mirror. I replaced the original roof-mounted mirror of my XJ40 with a Gentex auto-dim years ago, but that meant gluing a GM-style button to the glass, which can often fail. Since my windshield has just been replaced (I popped the roof mount mirror back in before the glass was replaced) I decided to do some modding.

The original XJ40 mirror has a ball socket on the backside, and a long arm which mounts into a bracket bolted to the roof.

It didn’t look to complicated to swap the XJ40 arm onto the X300 Donnelly mirror so I tried it.



The only snag was that the wiring for the Donnelly passes through the ball and up the arm. I decided to reroute the wiring through a new hole above the socket which meant splitting the mirror in half.

With a small flat-blade screwdriver, the plastic weld bond is easily broken.




The glass has to be removed too, which means gently prying it away from the back half of the mirror casing. It is attached with two adhesive pads. Steady even pressure here.





Now I was able to drill a new hole for the wiring.





After re-adhering the glass and supergluing the two haIves together, I gently popped the XJ40 arm into to the Donnelly mirror socket and replaced the metal securing ring. Looks fantastic!





And even better in the car! Such a big improvement over the glass mounted mirror; this is the way it is supposed to be!




The mirror sits at the perfect position and distance away from the glass unlike my Gentex which was a compromise due to the length of the arm.

Wiring is easy. Black is ground, White is 12v switched power, Grey is 12v when the car is in reverse (I left this disconnected, it just forces the mirror to be clear when in reverse, has never been an issue for me even with the Gentex)

Another little job done!