No brake lights when turn signal is on

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lomchivok

lomchivok

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wa.
68 Barracuda notch
I'm stumped.
All I wanted to do was install a repop stock radio...I did, it works. While I was at it I installed LED dash lights...they work too.
When I put it all back together and turned on the left turn signal it worked fine, the dash turn indicator worked too.
Flipping to the right, it sounded like something sparking under the dash when the flasher clicked on and off. The after market volt meter jumped erratically too when the right signal flasher activated.
Suddenly the sparking sound stopped. Now I have no right front turn signal but the right back works and I have no left back turn signal but the left front works and the right dash turn indicator light doesn't work...the LED is good.
The brake lights both work when the turn signals are off but when left or right turn signals are on both brake lights go out. All front and rear park, driving and marker lights work as expected.
All 4 emergency flashers work as well as both dash indicator lights. With the 4 way flashers on and stepping on the brakes the 4 way flasher stops flashing and the front park lights and rear brake lights and dash turn indicators stay lit up...normal operation.
After all of this I decided to install the new under dash wiring harness I have had for a while with new loud turn signal and loud 4 way flasher from O'Reilly Auto Parts.
With the new wiring harness installed I still have the issues mentioned above except for no sparking sound.
Prior to installing the new radio and dash light LED's everything worked fine except the left dash turn indicator light...now...well... it's all screwed up!
I have an original 68 Plymouth service manual...the 2 inch thick one...and have downloaded and printed an exploded view of the wiring harness. Everything in the new harness is correct with the old one.
2 weeks now of troubleshooting and still no joy...I noticed that all of the wires from the turn signal switch in the column have been crushed with the tan wire frayed but they all have continuity from end to end...I have a new switch with wires on order (shipped today)
I have taken a long wire from the ground post of the battery to the lights that wont work hoping to see a result but with no change.
Any help would be appreciated.
 
Offhand I'd say "the crushed harness" is the no 1 suspect. You should be able to access the TS connector and check right there and or at the kick panel connector and justify every circuit in the switch. Just look up in the diagram and get your colors, what you have is........

With the hazard switch on, (separate switch on those cars) that ties both fronts to the brake switch line, and feeds hazard flasher power in. So the hazards switch is 4 terminals, none are connected when off, and all 4 are connected when on.

At the TS switch connector, you have

flasher power "going in" to the switch

Brake light switch power "going in" with the pedal depressed.

Coming out is:

right front

left front

left rear and right rear are interconnected to the brake light switch WHEN CENTERED

left rear is connected to flasher when in left turn, and right rear still connects with brake light switch

Opposite of above is true when TS switch is moved to right turn.
 
Did you replace any of the out side bulbs also. Had a similar problem. I had to put regular bulbs back in the tail lights. I was told with all the led bulbs, there wasn't enough power to trip the flasher properly. changed them back and everything is happy again.
 
jlburg said:
Did you replace any of the out side bulbs also. Had a similar problem. I had to put regular bulbs back in the tail lights. I was told with all the led bulbs, there wasn't enough power to trip the flasher properly. changed them back and everything is happy again.
Click to expand...
thanks,
No, I only replaced the dash bulbs with LED's. All of the other bulbs are incandescent and test good.
 
67Dart273 said:
Offhand I'd say "the crushed harness" is the no 1 suspect. You should be able to access the TS connector and check right there and or at the kick panel connector and justify every circuit in the switch. Just look up in the diagram and get your colors, what you have is........

With the hazard switch on, (separate switch on those cars) that ties both fronts to the brake switch line, and feeds hazard flasher power in. So the hazards switch is 4 terminals, none are connected when off, and all 4 are connected when on.

At the TS switch connector, you have

flasher power "going in" to the switch

Brake light switch power "going in" with the pedal depressed.

Coming out is:

right front

left front

left rear and right rear are interconnected to the brake light switch WHEN CENTERED

left rear is connected to flasher when in left turn, and right rear still connects with brake light switch

Opposite of above is true when TS switch is moved to right turn.
Click to expand...
Well, I checked continuity of the turn signal wires and they are all good but I have a new one on order...should be here tomorrow.
I will check again tonight power in and power out at the turn signal switch and at the connector at the kick panel...this time I will write out my findings for future reference. I have tested so many things it's hard to remember what was what and with the frustration....it gets hard to think straight.
 
I actually write it down. Make yourself a "truth table." Go to the diagram, write down the colors and draw a picture of the column connector and kick panel connector.

Check the brake switch wire coming into the column connector. Should be hot when brake is pressed.

Check each rear wire LEAVING the switch. Both at the switch and kick panel connector, both left and right should be hot with brake switch depressed.

Now turn the switch one way or other. In left, you should lose rear brake light and left should flash

Opposite for right turn, etc.

These switches get AFU internally and can do really weird things.

As mentioned above check your bulbs.
 
67Dart273 said:
I actually write it down. Make yourself a "truth table." Go to the diagram, write down the colors and draw a picture of the column connector and kick panel connector.

Check the brake switch wire coming into the column connector. Should be hot when brake is pressed.

Check each rear wire LEAVING the switch. Both at the switch and kick panel connector, both left and right should be hot with brake switch depressed.

Now turn the switch one way or other. In left, you should lose rear brake light and left should flash

Opposite for right turn, etc.

These switches get AFU internally and can do really weird things.

As mentioned above check your bulbs.
Click to expand...
Thanks, good advice...I'll do that.
Does the circular dash wire connector labeled A thru K need to be connected to complete any circuits or can I test the voltages with the instrument cluster out and the connector disconnected?
 
BE CERTAIN your bumper is grounded well.
ADD a new ground wire if you need to make sure.
 
OK, I'll put my very best edumakated guess here with my quarter bet.
The smaller of the 2 circuit boards on your inst' panel has 3 contact pins in a straight line. The very top of those is the turn indicator. You'll find your screw up right there. Must be a dozen ways to attach this connector wrong. Plus pins pushed clear through the board, etc., etc...
 
Tested the turn signal switch last night... I have brake light signal to the switch. Brake lights both work with turn signals off. With either turn signal on, I still have brake light signal in to the switch but nothing coming out of the switch.

I have turn signal flasher signal in to the switch in both left and right position. No turn signal out of the switch to the right front but do have turn signal out of the switch to the right rear, dash indicator doesn't work and I have turn signal out of the switch to the left front but no turn signal out of the switch to the left rear, dash indicator does work.

With 4 way flashers on all hazard lights front and back and dash indicators work.

Looks like it's a bad turn signal switch...ordered one sunday, it should be here today.

Thanks everyone for your input and help...if the switch does come today I'll find out the truth tonight and post the results.
 
67Dart273 said:
^^ I'd say you found the worst of the problem
Click to expand...
I think so.
All of the wires are smashed leading up the column to the turn signal switch. The tan wire that feeds the right front turn signal (not working) is smashed and splayed open with exposed wires.
When this all started it was the right turn signal that caused the arcing sound and volt meter fluctuation. Pretty sure the tan wire being shorted to ground burned up some traces in the signal switch leaving me where I am now.

With the new wiring harness installed I was able to delete the crappy butt splices and hack wiring job done by the previous electrically challenged individual and made my own splices from the proper busses with solder joints and shrink wrap. You should have seen the rats nest of wires he had stuffed up there....unbelievable.... I still need to clean up his volt, temp and oil pressure gauge pack he put in then I will be done under the dash. I have a new engine compartment and forward lighting harness I will be installing next to remove the crappy wire job done there as well. I want that done before I get my new FiTech 600 power adder system in about 3 weeks.
 
Last edited:
Okay, so the switch hasn't arrived yet so I impatiently cut the switch out and took it in the shop to drill out the center retaining pivot peg to see what was going on. Hmm... it doesn't have traces but heavy (relatively speaking) spring wires held in place by locating grooves. the spring wires got hot in the short to ground, deflected the wires and burned a new groove in the plastic that held them from making proper contact. I was able to bend the wires back to their correct position and fill the melt grooves with JB weld for a temporary repair just to see if it would work again...it did and all turn signals and brake lights work as they are supposed to.

Hurry up new switch...I want to drive my Cuda again.

Thanks for the help guys...I learned quite a lot about the electrical system this time around.
 
Your JB repaired switch is now better than the one you ordered.
Epoxy won't melt away like thermoplastics.
Put the new one on a shelf for "someday".
Betcha never need it.
 
So my new switch came in finally. What a joke...the pivot pin isn't pressed in all the way giving about 1/4 inch movement up and down and there is continuity between the red and white wire (Brake and flasher wires). I tested it on the bench prior to installation against my repaired good one. the crimped terminal ends are weak as well...wires pull right off with little resistance. It's a crappy Shee-Mar switch. Got it from Ebay...should have known a 60 dollar switch would have been inferior to the Year One offering. So to Year One I went for a 160.00 dollar one... Should have went there first!!!
 
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