[HammerESQ]

Hello Everyone,
I'm having some issues sorting out the wiring in my 1977 911s, the PO made a mess of the wiring installing aftermarket alarms and stereo's over the years.

I've got most of it sorted, but I still don't have rear brake lights. I've confirmed that the bulbs and obvious stuff is okay, but I don't have +12v at the brake light switches on the master cylinder. Where do these switches get power from, what should I check next?

Thanks!