I've noticed that the electrical switches in Ford documentation are not well defined.
The turn signal documentation (in this case one specific to a 68-vehicle) actually have wiring errors so good luck following the factory manuals.
In the 68 switch I'm decoding I noticed the factory drawing has the brake light input to the switch labeled as a 10 when it's actually 511. 10 is the power into the brake switch and output for that goes into the turn signal harness from 511.
The connectors show 511 but the switch internal pics do not.
Although the colors and numbers are 68 related, the function of the switch is the same for earlier years if you remove the emergency flasher portion.
You can draw this in any number of ways. I originally started with a triangle like the manual uses. I instead found it clearer to show the make/break on the brake and turn signal circuit with some DPDT looking kind of switches. I also call the various circuits by their color number in this picture.
The functions of the basic part of the switch are actually fairly easy to understand.
The brake light switch itself is fed by non-switched circuit 10 from the headlight switch and its internal circuit breaker.
If the brake light switch has been closed (step on brake pedal), this sends current through the 511 circuit and into the switch. If you follow 511G from the bottom right, up the side and to the split you can see where it leads into both rear high output lights. Pretty simple.
If you move the turn signal to the left, for instance, this moves both of the 3 and 9 circuits to left as shown by the arrow. This disconnects the Rear LH 9 from the brake light 511 circuit and hooks both Rear LH 9 and Front LH 3 to an internal circuit that eventually runs to the T/S flasher 44 circuit.
How does the flasher side work? The flasher has switched power on the circuit 8 side and ground is found through the 44 circuit to the bulbs. In other words, the bulbs provide the ground for the flasher. This explains why the flasher will often fail or go very slowly if one bulb burns out or loses ground.
As for the brake light on the other side it still runs through the 511 circuit.
Things get real interesting on the emergency flasher side.
The three horizontal bars and the vertical arrow bar are all connected electrically inside the switch "tree".
The switch in the main part of the pic above is shown with the Emergency button off (pulled out).
When it is pushed in (second, lower box pic of switch) all of the horizontal bars move up. This disconnects the switched power 44 turn signal flasher and places the always-on power 385 emergency flasher into the circuit "tree". It also connects the front 3 circuit, the front 2 circuit and the 511 brake circuit to the emergency flasher. This causes all 4 of the lights to flash.
One thing about the circuit drove me crazy for hours since the circuit I drew had a major issue. It appears that if one presses the brake while the emergency flashers are on this will send a constant 12V
through the 511 circuit essentially turning all 4 lights on solid.
Finally I decided to find a battery and throw it into a 70 car. I had to see if this was true.
Sure enough, pressing the brake with the Emergency flashers on does turn all 4 lights on solid.
The horn is shown for completeness.
[edit punctuation]
