Did a search but did not come up with much. I have a 68 coupe with no brake lights. The running lights and turn signals work, so its not the lights themselves. I have 12V going to the switch under the dash, but when I apply the brakes, which activates the switch, the power drops to 0V. I replaced the back end wiring harness and everthing there seems to work as advertised. I did not replace the dash harness as it seemed good. As the 68 is home to the various mystery grounds for the wiper motor, is there one for the brake switch? I a wiring diagram, but seem to remember there was a resistor in there somewhere that is not in any diagram I have seen. Also, as much as I hate do do this job again, should I take the steering column and drivers dash section out to look for the short?
On a side sad note, I took it to a local restoration place here and they Bubba'ed it by jumping a wire from the fuse block to the brake switch. It worked for a short while, but blew the fuse it jumped from. They did great upholstery work, but Bubba'ed my wiring and I want to make it correct. Has anyone had this problem before?
Thanks

 

Your symptoms don't add up to anything concrete, but here's how it works in case it will help you troubleshoot.
12v is applied to the orange wire on one side of the brake switch and when brake is applied that connects the 12v to the white wire. This voltage comes from the fuse block on the fuse marked "stop/courtesy" or similar. There is a capacitor, not a resistor, attached across the brake switch contacts, but that is a noise suppressor for the am radio and is not necessary. The 12v on the white wire mentioned goes to the turn signal switch. When the turn signal switch is in the center position the contacts in the turn signal switch send the voltage to your brake lights. When you turn the turn signal to one side or the other, the brake light voltage is interrupted inside the turn signal switch and the 12v flashing voltage is substituted that comes from the turn signal flasher. If your turn signal lights are working, everything from the turn signal switch to the rear is working, including bulbs, grounds, everything (same wires). The first thing you have to get is the 12v from the orange wire on the brake switch to transfer to the white wire on the other contact. I'd remove the capacitor for troubleshooting if it's there, it's unnecessary. If your voltage drops to 0 when you press the brake the brake fuse should blow immediately. If it does not, you may not have a short, but rather a problem with the voltage from the fuse box may be not making it through the fuse. Change that fuse first.
One other item that I am not familiar with on a 68 is the role the emergency flasher plays in that setup. I don't know if removing it helps or hurts in this case. Sorry about that part. As I said, your first step should be getting 12v through the brake switch, without that the brake lights will never work.

 

65GGvert, Thank you for that. As that wire is hard to get to, would you partially remove the dash to check it? Its never the easy wire to get to.
Thanks again.

 

I would not, but I have never had to remove the switch either. I would have thought you could reach up to the brake pedal lever and check the voltages. Check it on the white wire that goes up into the column to the turn signal switch connector. The very first thing I would do is put a voltmeter on the stop fuse and verify 12v on both sides, with and without the brake pressed. Post back and we can go from there. Sometimes those fuses melt at the connection to the end cap and the fuse itself looks good, but is not.

 

Lobzilla, if you're going exploring in the electrical system, I highly recommend getting a Power Probe III. No Automotive Electrical Pro, would be without this tool, to diagnose electrical problems in a car. It's all of $85 and I'm sure you spent that already in 'personal time' and aggravation.

You hook it up to the car battery (it's got a nice long cord, that is soft). It will light up, beep and tell you, that you have 12V, ready to go. When you check a circuit, it tells you instantly, whether you even have a complete circuit or not (small green LED will go on, in the corner of the Power Probe III) or it will be red.

You can apply 12V or even ground, anywhere on the car. You can even test bulbs, right there in your hand, with the side ground clip. Just keep applying power with the rocker switch as you go back from the taillights till you find out where you're not getting a 12V.

It will also beep loudly, whenever you find good voltage and the large green LED will light up and it will put the voltage on the LCD screen. Great for under the dash, because you don't have to 'read' the screen to get a verification, unlike a multimeter, which is great for under the dash. Because you only have to listen for the beep and see the green LED. It also has bright white LED's that illuminate the area you're working with, very nice, especially in the dark, so no, you don't necessarily have to disassemble the dash to get to the electrical. And unlike the multimeter, you don't need to find a ground, as the probe is already grounded to the battery!

It doesn't have a 5 star rating from over 400 users, for nothing.