On the rear bulbs that are dual fillament and act as directional signals and as tail and stop lights, what makes them get brighter as the brakes are applied. I am trying to figure out how to wire the brake light switch on the pedal into the harness that I am making. The turn signal wire comes in from the column and power comes from the headlight switch on the dash. The only other wire on the bulb sockets is for the ground. What makes it get brighter when the brakes are applied? Do I splice the brake light wire into the power wire from the switch (more power = more light)? What do I do here?

On the rear bulbs that are dual fillament and act as directional signals and as tail and stop lights, what makes them get brighter as the brakes are applied. I am trying to figure out how to wire the brake light switch on the pedal into the harness that I am making. The turn signal wire comes in from the column and power comes from the headlight switch on the dash. The only other wire on the bulb sockets is for the ground. What makes it get brighter when the brakes are applied? Do I splice the brake light wire into the power wire from the switch (more power = more light)? What do I do here?

There are two completely separate circuits involved. The only thing they share is the negative connection at the bulb socket.

Think of it as two light bulbs in one glass case, with a common ground/negative.
If you look carefully, one of the filaments is nearly twice the thickness of the other. This is the stop/turn side (thicker filament glows brighter).
With just the taillights on, only the small filament is on, and stays on regardless of what you do with the brakes or signals. When the brakes or turn signals are applied, the large filament is energized - so it "appears" that everything gets brighter.

http://auto.howstuffworks.com/turn-signal.htm

There are two completely separate circuits involved. The only thing they share is the negative connection at the bulb socket.


There's actually 3 circuits, isn't there? Or maybe I should say 2 1/2. The brake light and the blinker are two circuits that share the same filament and some of the wiring.

The way it works is that the wire from the brake switch runs through the turn signal switch. The part of the switch that operates the brake light will normally be on, but will break the brake light circuit when you turn on the blinkers. So when the brake lights are on, and you turn the blinkers on at the same time, the brake light is actually turned completely off while the turn signal is on.

The part of the switch that operates the brake light will normally be on, but will break the brake light circuit when you turn on the blinkers.

How? I am not using any stock wiring. I have a brake light power wire that is hot when the pedal is applied, a tail light power that is hot when the headlights are on, and the two seperate turn signal wires. How do I hook it up to the tail lights?

The tail lights are on their own harness (stock) which has 5 wires going into it and the harness itself has its own ground which is not one of the 5 wires. How do I hook this up to the 4 wires I mentioned above?

Putting it another way;

When the the stop light switch is made closed it sends power to the brake light filaments VIA another switch inside the turn signal switch.
It is not sending power directly to the lights, only to the turn signal switch.

That switch inside the turn signal switch shuts off the power from the brake light switch to whichever side needs to be blinking.

The standard dual filament bulb socket(1157 type bulb) usually has two wires attached. One wire is for the tail lights(brown) and the other wire is for the stop/turn wire(right turn/stop is green, left turn/stop is yellow). The socket usually grounds itself if the socket hole in the tail light is metal, or if the socket is plastic, it will have a large metal ring that sandwichs itself between the socket and the tail light housing and will have a wire attached to be connected to a ground source.

So, going to the rear you will have a yellow wire for the left turn/stop, a green wire for the right turn/stop, both of these wires originate from the steering column. You will have a brown wire for the parking lights coming from the headlight switch, and you may have a light green wire for the backup lights.

As stated by others in the previous above, the wire from the brake light switch that is hot when the brake pedal is applied goes to the white wire at the steering column. If you apply the brakes, with no turn sign activated, then the power from the brake light switch goes thru both the yellow and green wires to the rear tail lights to the bright bulb filament to indicate a stop situation, regardless if the parking lights are on or not. If you activate the turn signal switch to indicate a right turn and apply the brakes, then the brake light power only flows thru the yellow wire to the rear to activate the left bright bulb filament, the turn signal cam in the steering column blocks the brake light power to the green wire and power from the flasher is now diverted thru the green wire to the bright bulb filament to indicate a turn condition.

The brake power has to go thru the steering column to the rear tail lights so that the turn signal switch in the steering column can redirect the necessary power based upon if a turn signal is applied or not.

Don

Now I understand. I couldnt grasp the concept of what made the turn signals take priority over the brake lights but that was when I was under the impression that I could run power from the stoplight switch directly to the bulbs. Now I know that it is all taken care of inside the column. Thanks for the help guys!

I wired a -63 Nova from scratch once, and I had a hard time understanding this until I happened to find the schematics in a car magazine. It was very simple, once I realized that the blinker switch also contains a second switch that breaks the brake light circuit.