No Brake Lights or Turn Signals. Where to look next?

[kcpope]

Well, sorry to dominate all the recent forum activity, but I’m really trying to get this thing done!

 

I’ve got an electrical problem somewhere. I’ve read what feels like 100 posts regarding the turn signals. I’ve studied the following links heavily and still can’t seem to figure it out:

 

https://www.classiczcars.com/forums/topic/16435-72-240z-brake-light-wiring/

 

https://fiddlingwithzcars.wordpress.com/2013/01/20/hazard-switch-brake-light-turn-signal-circuit-analysis/

 

THE PROBLEM: I have no brake lights or front/rear turn signals

 

HERE’S WHAT DOES WORK: Hazards (front and rear), Headlights & Tail lights, Reverse Lights, Brake light switch, all fuses are good, all light bulbs are good,

 

Turn signal switch was just rebuilt, as well as combo switch. I meticulously cleaned everything, lightly sanded all the contacts, dielectric grease, the whole 9 yards. I sanded down my grounds both at the firewall and at the rear under the gas tank.

 

I followed the directions from the first link I posted above and verified that I have 12 volts at the Green/yellow wire that goes from the hazard switch to the connector for the turn signal switch. Picture below. I also verified that the voltage goes to zero when the brake pedal switch is pressed, telling me that the brake switch is working.

 

Again, according to that first link above by 72SLOZ, that should indicate that my problem is something downstream of the hazard switch.

 

When I plug in the turn signal switch, I don’t get any voltage from the green/yellow wire to the white/black or white/red wire. This might seem to indicate a problem with the turn signal switch?

 

BUUUUT, I thought to myself, I’ll bypass the turn signal switch and just insert a jumper wire into the connector shown below and see if I get any lights, still nothing!

 

I have my multimeter in hand. Any idea where to look next?

 

 

 

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[SteveJ]

If the switch is disconnected from the brake pedal while the turn signal switch is in the neutral position, you should see 12VDC to ground at the points indicated below.

If you don't, that means the switch was not rebuilt properly.

Under those same conditions, you should have 12VDC to ground at the green wire in the picture above.

Please confirm that.

[kcpope]

Steve, thank you. Tomorrow I will test like you said and report back.


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[kcpope]

Alright, check out the video I made here explaining the results of my test, amongst other things. Easier to explain with video…

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[SteveJ]

Take some clear photos of the 6-pin connector on your turn signal switch so that we can see the wire colors.

Also, when you plug the two halves of the connector together, look for movement in any of the wires. You might be pushing a wire out.

If you had a good ground, you should have seen battery voltage to ground at the green/yellow wire.

 

[kcpope]

Connections are all solid. No wires being pushed out. It’s like when I plug in the connector the GY wire just stops supplying 12V.


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[SteveJ]

So now it's time to look upstream. I suspect you have some corrosion, poor connection, or a loose connection somewhere in the circuit. That improper current path is a choke point, and you see the voltage drop to nothing. You could try some things like jumpering out the brake switch and see if you have brake lights. 

Also measure the voltage to ground at the fuse for the brake circuit before and after connecting the turn signal switch. 

[kcpope]

When I connect a jumper wire connecting only the two green/yellow wires together, I get 12 volts at the proper terminals on the turn signal stalk (but still no brake lights). See explaination video here…

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[SteveJ]

Your results don't surprise me. In fact, it supports what I said in my previous post.

You have a problem in the circuit that is restricting current flow between the battery and the turn signal switch. It won't show up as a problem using a voltmeter because the voltmeter is a high resistance device that doesn't require much current. The restriction shows up as a loss of voltage when the circuit is complete.

It's late for me. I should have a chance to give you some more diagnostics tomorrow. Maybe I can even make a demo video to illustrate my point.

[kcpope]

Your results don't surprise me. In fact, it supports what I said in my previous post.
You have a problem in the circuit that is restricting current flow between the battery and the turn signal switch. It won't show up as a problem using a voltmeter because the voltmeter is a high resistance device that doesn't require much current. The restriction shows up as a loss of voltage when the circuit is complete.
It's late for me. I should have a chance to give you some more diagnostics tomorrow. Maybe I can even make a demo video to illustrate my point.

Understood, thanks for the explanation. Oh man, a demo video or even just a list of what to test next work be great!


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[SteveJ]

I couldn't pull off the simulation well enough to suit me.

First, look for corrosion. Where? Look at the PDF I attached. I indicated 4 areas to focus on, numbered in red.

Inspection Points.pdf

This is a visual inspection only. You're meter isn't designed to ferret out this kind of problem. For the fuse box, examine the contact points of the fuse holder, and you may need to remove the fuse box to examine the back side of it. Just be sure to pull the negative terminal off the battery before you attempt to do that.

Sometimes disconnecting and reconnecting connectors cleans off enough corrosion that the circuit will work again. You may also want to try to jumper out the brake switch to see if that is the culprit. You can probably do that with a couple of bullet connectors and a short piece of wire.

[zKars]

Turn signal light issues, especially those that exist while the hazards work just fine, are often the fault of the hazard switch. Remove it and clean its internal contacts and check for solder problems where the wires attach.

Also make sure the battery is fully charged or the car is running, or attach a charger to the battery while you do testing. Low voltage often causes older flasher units to not want to do their job well or at all making diagnosis of related problems difficult.