ignatz

The driver's side brake light on my 69 only gets 6 volts and barely lights up. Here's the situation (voltages approx.):

1) I have LED's back there, just as a point of information. The flashers are all solid state replacements.

2) Original harness but all of the grounds have new ring terminals, the housings are clean and freshly galvanized.

3) Have removed the cabin harness tape wrap and traced all of the wires back to the connector by the air vent. No shorts or broken wires.

4) If I open the above connector and jumper just the brake light pins, the light gets 12 volts and lights just fine. Suggests there is some interaction with the rest of the wiring when connected.

5) With the connector mated, if I turn on the passenger directional, the driver brake light also works just fine, getting 12 volts. Maybe something to do with the directional switch assembly? But ...

6) ..thinking maybe it is some kind of weird short in the directional switch in the (non-tilt) steering column, I replaced that with a new one. No change.

7) Last thing, if I put a voltmeter on the brake light signal and depress the pedal, the signal momentarily goes to 12 volts and then jumps down to 6 volts, as though there is something with a time constant like a capacitor or a physical delay that is coupled to the brake signal. And again only when the passenger blinker is off.

Everything else works back there, passenger brake, tail lights, hazards, directionals.

Any suggestions, anybody?

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I guess I wasn't completely out of ideas. After writing this I thought to make some measurements on my old directional assembly. There is a black wire with a white stripe that connects to the brake pedal switch and the two next wires in the connector connect to the brake lights, green and yellow or black coded yellow. There is a difference in resistance to the brake light switch, a couple of K ohms to the green and a couple of ohms to the yellow. don't see how this makes sense. All I can see are copper contacts in the assembly. Cleaned all the contacts in the old assembly with contact cleaner spray. If the new assembly is like the old, there is a different resistive path to the two brake lights.. If this is the way things are supposed to be, it must only work right for incandescents???

oledave60

This is just a thought. If you have one of these capacitors spliced into your brake wires, you might try disconnecting it. Again, just a suggestion.

ignatz

Snipped a lead, no change, but thanks. I assume that is there for the radio, think I can leave it off without a problem.

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Funny thing about that, removing the cap did nothing but when I started wiggling the harness both brake lights came on. Possibly the splice is marginal. At least I am closer to the problem!!!!

ignatz

oledave60, you can feel good about helping someone today. I popped the splices off and looked at the cut they made. Hard to tell for sure but I would guess only 2 or 3 strands in that 14 Gauge wire were intact. My best guess is that only one of the taillights was all that wire could support. The other only flickered. I'm imagining all those little electrons just getting bunched up trying to get through. I guess the factory did this to me.

Anyway, cut and spliced the wires back together and both lights are on and bright as can be.

oledave60

Sometimes you get lucky. Glad it helped. Dave