@genebaby: The Grey wire that terminates on pin#10 on the rotary light switch is what is known as a "Terminal 58" (T58 ) supply - which simply means in DIN 75552-speak that it's instrument illumination voltage source. On a mk7, the car's T58 rail is generated by the BCM on pin #62, socket C - this wire runs to multiple points inside the cabin to back-light the myriad LEDs inside various switches (including the rotary light switch)
As you may be aware, illumination of the the instrument cluster clocks and lot's of other switches via the T58 supply is controlled by a photo-transistor that sits between the "7" and "8" numbers on the rev-counter (see picture below)
Grab a torch and shine it into the area shown, the clocks should increase in intensity (as should a number of back-lit switches inside the cabin.
The job of the photo transistor is to modulate the value of the T58 voltage-rail according to the ambient light levels inside the cabin - so at least on a mk7, no there is nothing normal about a 12V T58 rail!!
Don
Please don't PM to ask questions about coding, or vehicle repairs. The better place to deal with these matters is on-line, in the forum proper. That way you get the benefit of the expertise of the wider forum! Thank you.
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