Left brake light goes out when right blinker on??

[JJorgensen52]

Okay, I've been thinking on this one a bit but I got pulled over for it last night so time to figure it out:

My truck has the original turn signal switch. All the light functions work independently: hazards, left and right turn, running lights, and brake lights.

When I turn left, everything is normal. When I turn right, the blinker works fine with the running lights, but as soon as I apply the brake, the left running light goes out and no brake light comes on. The right light continues to blink as it should.

I've checked connections, grounds and bulbs in all the lights and everything is OK. Only think I haven't done at this point is replaced the flasher or the turn signal switch.

Is this something I can fix (bad contact or something sticking in the switch) or is it just time to order a replacement?

[mgchevyparts]

You have a bad ground

[VetteVet]

Disconnect the steering column connector and get a multimeter. Place the red lead on the white wire on the end of the connector, then place the black lead on the yellow wire for the left turn/brake light. Put the meter in the ohms range and test for zero ohms with the turn signal switch in neutral. Put the black lead on the dark green wire which is the right turn/brake light and test for zero ohms. If you get zero ohms both ways then place the turn signal switch in the right turn position and the meter should read infinity or open.

Now place the black lead back on the yellow left turn/brake wire and with the signal switch in the right turn position the meter should read zero ohms. If it doesn't then there is an open connection point in the turn signal switch in the brake circuit.

You might be able to clean the switch points with contact cleaner and solve the problem.

[68C15]

Originally Posted by mgchevyparts

You have a bad ground

yep
bad grounds on tail lights is as common as finger nails. I usually solder a wire to back of light housing and run it to a ring terminal and self drilling screw into clean metal on frame

[JJorgensen52]

Originally Posted by 68C15

yep
bad grounds on tail lights is as common as finger nails. I usually solder a wire to back of light housing and run it to a ring terminal and self drilling screw into clean metal on frame

Even with a separate ground (ran one during testing) it still did it.

I'm going to do the checks VetteVet suggested above tonight and report back

[BigBlack]

Just this morning I got mine fixed, now i'm not sure if it will help you but one of my grounds was loose on the back of my dash cluster(on the printed circuit board). Now when I say ground is just a 5/16 screw that grounds the board... maybe something to check not sure. Did have problems with grounds on tail lights and all marker lights, so like mention before I soldered some new grounds in and I was good to go.

[Coley]

Originally Posted by JJorgensen52

Even with a separate ground (ran one during testing) it still did it.

I'm going to do the checks VetteVet suggested above tonight and report back

Also, here is an easy check:
-Remove both back light covers and remove the (dual circuit) taillight bulbs and inspect them and their internal filament circuits closely.
The backstory on this is that if one of the filament circuits within the taillight bulbs fails it sometimes flicks over against the other internal filament and causes all sorts of circuit/power path problems. (ask me how I know....LOL)
If you have a spare bulb (1157 I think), use that as a correct/new test bulb for this type of incident and try it in both back lights.
This is a real quick, clean, easy check and shouldn't take more than 5 minutes.
Keep us posted and good luck.
Coley

[Tinkermc]

It is a bad ground and please remember you can NOT create a ground with a test lite.

[68C15]

Originally Posted by Tinkermc

It is a bad ground and please remember you can NOT create a ground with a test lite.

exactly!!!! That's why I have a Power Probe III. If you use one, you'll fall in love with it and wonder how you got along before.

Test lights are good for one thing and one thing only. Testing to see if the test light bulb works

[JJorgensen52]

I have isolated the problem to the turn signal switch itself:

Turn signals off, I have continuity from brake switch to both left and right taillights

Left signal on, I have continuity from brake switch to right tail light only, and turn signal circuit to left tail light

Right signal on, I have NO continuity from the brake switch to the left tail light, and I do have continuity from the turn signal circuit to the right tail light.

This was tested at the connector, with the lights out of the circuit.

I don't have a steering wheel puller here, but I will hopefully be picking one up in the next few days to take care of this.

Thanks for the help.

[JJorgensen52]

Problem solved!

First off, for those that said check your grounds - while it was not the source of this problem, I did in fact find my taillight housing screws loose and causing the running light to blink on and off. Tightened them up, all set.

Now on to the original post:


See between the horn contact post and the shifter in the top of the column, about 2 o'clock? There is a little teeny plastic tab on the turn signal cam which limits the travel. In the photo, you can see the lower one at about 4 o'clock (right turn) broke off on my truck, which allowed the cam to actually go TOO FAR to the right, past the taillight contact, breaking the circuit.

Easy way to diagnose this: push the turn signal stalk towards the side that's having trouble, but not all the way there, and see if the brake lights work.

I purchased a replacement cam at the local parts box and voila! lights all work as they should. That said, now my turn signal cancel feature doesn't work - it's like the new cam is slightly larger and doesn't quite engage the cancelling cam? Anyone had that problem?