Left brake light not working

[skokie]

I just had a bad turn signal switch replaced in my tilt column but now the left brake light is not working. Blinkers and the right brake light are working fine. Any thoughts on what could cause this.? Also the wiring harnesses from the cab to the back lights are new. Which wire in the U harness controls the left rear brake light?

[Andy4639]

Take the light assembly out of the truck and check the wires for ground with a test light. Does it blink when you turn the signal on? More than likely a ground problem.

[skokie]

It does blink when I turn the signal on. Just no brake light.

[VetteVet]

Your problem is in the turn signal switch. There is a jumper between the left and right turn signal wires that operates the brake lights when the turn signals are not in use and disconnects the power to the brake light when that turn side is used. The turn lights and brake lights use the same circuits so if the brake lights work or the turn lights work then the bulbs and grounds are good.
Here is a schematic.

[skokie]

I just tried a new brake light switch and got the same thing. I was looking at the diagram and I dont see the jumper you are talking about. Can you highlight it?

[Longhorn Man]

your problem is probably in the new turn signal switch you installed. Put your foot on the brake (engine off, key in off position) and look over your shoulder at the brake light shining on something, as you are looking over your shoulder, wiggle the surn signal lever, and even put it in left then right signal location. Does the bum brake light come on at all?

[68 P.O.S.]

Check the switch for a pinched wire inside of the column. That happened to me once.

[VetteVet]

Originally Posted by skokie

I just tried a new brake light switch and got the same thing. I was looking at the diagram and I dont see the jumper you are talking about. Can you highlight it?

Sorry I can't show you the jumper cause it's built into the turn signal switch. I posted the diagram to show you what color the wires were that went to the turn signals. Left is yellow ans right is dark green. If someone you paid installed the new switch then it's on them to fix it. I'd take it back and say here ya go.

[skokie]

Vettevet I did pay someone to install the switch.

68 POS I will check it out and see if anything is pinched.

Longhorn Man I will try that out and see if I get anywhere after I check for a pinched wire.

[Boog]

Morning Skokie. I don't know what all you have done so far but I suggest using a test light at the rear to first see if there is power getting to the rear and backtrack from there to the front. It can very easily be a bad connection at the U shaped harness connection. If you don't have power down that far from the turn sig switch then it is in the switch or its harness.
Was the turn sig switch replaced to fix this brake lamp problem?

[skokie]

Turn signal was replaced due a bad one that came with the column. I checked and I do not have power when the brake light is on but I do have power with the blinker going. I unhooked the U connector and checked all of the wires/connectors and they look good. Looks like it is making a very solid connection when you hook both sides up. I checked inside the column and I dont see any pinched wires etc. Not sure what else there is to check.

[Boog]

What about back probing the wires on the turn sig switch side of the U connector? It's possible to have a bad crimp on terminal and even though that's a new sig switch don't mean it's not a bad one. I've bought new parts before that didn't work.

[skokie]

I could give that a try. Its the green adn yellow wires correct? If I use my multimeter I show show 12v right?

[Boog]

I believe the green and yellow wires are the turn signal wires which you said worked fine. I've looked at that schematic VetteVet posted but my eyes cannot determine the brake light wires's color. I believe it's brown but not 100%. The lamps do operate on 12V. I use a test lamp mostly. Pointed tip with a bulb in the handle and an alligator clip on the wire to ground it. Easy to use, pierce the wire and bulb lights up when there's current.

[skokie]

Ill give that a try and see what happens.

[68 P.O.S.]

Do you have a coil or leaf rear? If you have coils, check to see if the wire is pinched between the spring and the retaining cup. I had this happen as well.

[Longhorn Man]

as stated before, the green and yellow are brake light AND turn signal wires.
If a wire was pinched any place after the steering colum, the blinker would not work period.
Did you try the watch and wiggle/oporate the signal switch I pointed out before?

[skokie]

Originally Posted by Longhorn Man

as stated before, the green and yellow are brake light AND turn signal wires.
If a wire was pinched any place after the steering colum, the blinker would not work period.
Did you try the watch and wiggle/oporate the signal switch I pointed out before?

Yep I missed that one I did try the wiggle and no change.

[wskibnt]

This is a great site! I was having problems with my brake lights and turn signals and thought it was in the sockets and cleaned and still no brake lights.Came to this site by chance and read a few posts about my problem and found that my problem was,you guessed it the blinker switch.Pulled off the wheel and cleaned the contacts and now they are all working.I just want to thank all who post on here because without you I was considering a new wireing harness.
I have a 72 C-10 that I like a whole lot and with this site I will be able to get it back into shape
It was the wiggle test and a mirrow that helped me figure it out