The electric operation of the late model CX-type mirrors on my Excel became intermittent and then stopped working altogether. Since both mirrors were affected, and the supply was OK, I isolated it down to the switch.
Rather than worn/dirty contacts as you might expect, the fault with the switch was that there were dry solder joints between the connector pins and the printed circuit board on the back of the switch. You can get at the solder joints by carefully prising out the pcb from the back of the switch, there is no need to remove the buttons on the front. Be careful not to lose any of the metal "dumbells" (thanks for the apt description in a previous post Angus!) that form the switch contacts. Any other secondhand switch is likely to have the same problem, and no amount of WD40 or similar is going to help.
You can just "reflow" the solder on each of the pins, making sure that is has adhered to both the pins and the pcb. However a better joint can be acheived by removing the old solder (using a solder sucker or braid, from Maplins etc.), applying some liquid flux to ensure good flow, then resoldering the joints from scratch.
Refit the switch with the mirror selector to the top, otherwise it all works backwards... DAMHIKIJKOK!
Job Done!
Glad I got the old one going!
