Thanks @
Mach1 Driver
You're right... once you've thought through it, its not too hard.
Fortunaley, I had the old turn signal switch assembly to kind of futz around with and test wiring into/out of. The only thing bad about it was the cancelling tangs - so electrically it was fine.
I'm just home from fixing the brake lights. Problem solved. The problem was in the wiring. A victim of my aging eyes, 50 year old wiring and overspray.
I was wrong when I said it was caused by me messing with the wires to change the flasher. This dates back to me changing the turn signal switch and I never noticed my mistake. I would swear to you I tested the brake lights and they worked, but there is no way that's true. Fortunatley I've only driven the car around the block this way.
I used a combination of the averagejoe site I referenced earlier, in conjunction with the wiring diagrams from Veronica's blog,
The Care and Feeding of Ponies: 1966 Mustang wiring diagrams Even though they say 66, the colors are the same for the 68. Unfortunatley, I'd gone to work on the car before I got to
@Mach1 Driver 's list.
As I mentioned earlier, I was testing continuity - you could do that or voltage. I'll step through it using voltage in case anyone else finds this topic and needs the help.
12v comes from the headlight switch, which is fed directly from the battery. No fuses. The headlight switch has an internal circuit breaker, I've read.
That 12v goes to the brake pedal switch on a green wire with a red stripe, wire #10 on the diagram. Reach up there with your meter or test light and probe the back of the connector. Should be 12v. If you don't have 12V, go back to the headlight switch.
It should be hot all the time.
It comes out of the brake pedal on a green wire, #511 and goes through the curved turn signal switch connector and up to the turn signal switch.
If you don't get 12v when you press on the pedal (again, probe the back side of the connector while pressing down on the brakes), investigate the switch. Might be coming apart, might have failed wiring, might be out of alignment, might need a shim. Lots of discussion on that elsewhere on the forum. As I mentioned yesterday, mine worked fine.
From there, you can pull the connector apart and check the green wire pin in the curved connector (make sure you're checking the chassis side, not the one going up to the switch), In the curved connector, its going to be in the bottom (shorter) row 1 in from the end. If you have 12v here, carry on. If not, check the interity of the green wire between the brake pedal switch and the connector. This was not my problem.
With the curved connector re-connected, press on the brake pedal with the emergency flashers off and the turn signals cancelled (in the center, neutral position). When you press on the brakes, you should have 12v at both the Green with orange stripe (#5 on the diagram, Right hand brake light) and Orange with Blue stripe (#9, left hand brake light). If you enable the turn signal switch with the car off/key out, you'll lose 12v on one of the wires - as its killed the 12v from the brake light switch, so when the flasher is working (its not, key is off in this test), it isn't backfeeding or shorting things out.
That's really the "magic" of the turn signal switch, is killing the 12v from the brake lights so you can have turn signals instead, since this is a single bulb system.
If you turn the key on with the turn signal switch activated, you'll get pulsing 12v out the side that's signaling and steady 12v from the other side (assuming you've kept activating the brakes).
That's what wasn't working for me. I had 12v in the 511 wire but did not have 12v coming out either leg to the brake lamps when pressing the pedal. I did get (varying) 12v with the turn signals activated - so I knew the wiring through the car and the bulbs were all good.
So, I proved what I set out to do - which was be sure the failure was in the expensive turn signal switch and not just some broken wire under the dash.
I disassembled the column and started looking for a broken/bad green wire or something obviously wrong with the switch. I started by verifying the position of the wires in the connector.
Remember I told you the green wire 511 is one position in on the bottom of the connector? Well, right next to it is a green wire with a white stripe, which is the turn signal bulb for the left front turn signal.
If you've got old eyes and wires that have 50 years of dirt and overspray on them, that old 511 green I pulled out of the connector with the old turn signal switch sure looked like green with a white stripe. Though I was carefully and only did 1 wire at a time, I still screwed up. I swapped Green and Green with a white strip - 511 and 50.
Once I changed those two (which is a pain, though I understand how to unpin connectors I am not good at it)- everything worked fine. The left front signal I assumed was a burned out bulb even works!
So thanks all for the guidance and assurance that the diagrams would help me chase it down and that the problem probably was up in the column.
While mucking about with all this I discovered the master cylinder is wet. Not enough to be dripping but wet enough to need replaced. I'll need some help with that, since I've no idea what this master cylinder is or where it came from. In another thread, after I research.
Thanks again,
Scott
