Brake light mystery

[CaptGrandpa]

The brake lights on my ‘68 912 targa are not working. All other lights are working fine. I pulled the right side tail light housing and the bulb looks good. When we step on the brake pedal there is power to the light, although it is only about 11v. I would normally blame the bulb, but since both lights are out that seems unlikely.

[wkrtsm]

1. Has there been any body work or collision work done on the vehicle recently?
2. Problems with front turn signals, night driving lights (under amber lens) will impact rear lights as well. (trust me, i spent several hours chasing down why my night lights in rear weren't working and had low voltage, which was due a problem with the front turn signal assembly).
3. It could be the brake pedal switch under the dashboard.
4. Also, pull the fuse for the brake lights, clean the terminals, and maybe replace the fuse.
5. Disconnect the brown ground connector on the brake light housing assembly, and reconnect it, then try a voltage measurement. Do the same for the positive wires that connect to the brake light bulb assembly (which snaps out of and into the assembly). The left brake light bulb assembly has two positive wires, and the right has one positive wire.
6. Voltage conditions for all rear bulbs are inextricably connected to anything that can happen with front bulbs, so as an FYI - there's no free lunch -- if you don't find something immediately. In other words, issues with any front lighting can be causal for rear lighting problems, and vice versa. Headlights/wiring do not usually affect night driving light, brake, or turn signal issues.