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I have '67 malibu when the headlights are off the brake lights work.At night when I turn the headlights on the taillights come on and stay on but when I press the brake the brake lights never come on. I haven't had a chance to dig into it yet I was just wondering if anyone might have seen anything like this before and might steer me in the right direction.
 

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This might be obvious, but it could be the bulb. The bulb has two elements-one for the tail light, one for the brake light. Maybe, one element is burned out. It's easy to see by looking at the bulb.
 

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That is strange. The tail light and brake light are on different circuits, so turning on the lights should not cause the brake lights not to work. I would check a couple of things. First, make sure that you have the correct bulbs (I use 1157, or 2057). Second, check that you have a good ground on the quarter panel extension. Take one or two of the nuts off that hold the quarter extension on and clean any paint off of the body where the extension studs come through, so that the nut will ground the extension to the body. Also clean the socket in the extension, where the conector goes through.
Do the turn signals work with the lights on?

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You have a bad ground at the tail/stop lights. Clean up the tail light housing mounting area or run a wire from them to a good ground source.
You could check it with a wire with alligator clips on it first.
 

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<BLOCKQUOTE>quote:</font><HR>Originally posted by Dean:
maybe the "tail" and "brake" wires are reversed and when the headlights are on, the brake lights are also on
The brake lights (now tail light filaments) would not show because they are dimmer
<HR></BLOCKQUOTE>
Dean
Give you something to think about. It's an open ground like Old Longboarder mentioned.
Think about the circuit this way. Assume an open ground to only one of the rear sockets.
Light bulbs are only resistors. They are basically Tungsten and have a very low resistance value if you measure them with an ohmmeter. The 1157 lamp has two filaments that are tied together at the base (ground). You have 2 series resistors that are different values. If the base is not tied to ground you only have 2 connections to the lamp.
If you apply 12 volts to the brake filament, without the ground to the lamp, it can light. It finds ground through taillight (running) filament "resistor", through the other rear tail light lamp "resistor" (brown wire goes to both lamps), and then to ground.
This work fine until you apply 12 volts to the tail lights (brown) by pulling on the head lights. Now the brake filament can't light because you have near 12 volts on each side of it. 12 volts applied to yellow/green and 12 volts applied to brown.
Have a safe trip.
John
 
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