Author Topic: Brake Light Testing - Turn Signal Switch  (Read 1091 times)

rmarble57

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Brake Light Testing - Turn Signal Switch
« on: November 27, 2019, 10:48:06 AM »
Looking for some technical wiring help for non working brake lights.

1967 GT350. 
Brake lights just quit working. 
Turn Signals work fine front and rear. 
Tested the switch on the Brake Pedal and that is fine.

Illustration:
Push on the Brake Pedal with or without the headlights on and no Brake Lights.
Left and Right Turn Signals both work front and rear
Push on the Emergency Flasher switch and the front signal lights work and blink, but the brake lights do not.
Push on the Brake Pedal while the Flashers are on and the Front Signals go on solid and still nothing on the rear.

Can anyone shed some light on how to test what might be wrong?  I'm thinking it may be a failure of the turn signal switch, but don't know how to diagnose.  With the signals working, I know that it isn't anything to do with the wiring back to the bulbs, and with the brake switch affecting the emergency flashers, I know that that portion of the brake switch is working.

The turn signal switch is about 2 months old and purchased through a Mustang parts vendor.  Assuming it is a Scott Drake piece.


Would appreciate any advice.
« Last Edit: November 27, 2019, 11:35:53 AM by rmarble57 »

67350#1242

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Re: Brake Light Testing - Turn Signal Switch
« Reply #1 on: November 27, 2019, 11:37:24 AM »
I had a similar problem and found poor connection of the TS connector at the steering column.  Try disconnecting/connecting the plug or jiggling it around while brakes are depressed and see if you have an intermittent connection.  I had to recrimp all the pin connectors in the TS harness to fix mine. (under dash harness side)
Kurt.
67 GT350  SJ 02/01/67  Gray 4spd A/C
67 Coupe  SJ 11/16/66  White Auto A/C PDB

Bob Gaines

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Re: Brake Light Testing - Turn Signal Switch
« Reply #2 on: November 27, 2019, 11:50:00 AM »
While your at it double check to make sure you have a good ground on the taillight harness in the back. The ground coming out of the Mustang harness. Bad ground has been the culprit of many problems with 67 taillights.
Bob Gaines,Shelby Enthusiast, Shelby Collector , Shelby Concours judge SAAC,MCA,Mid America Shelby

JWH

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Re: Brake Light Testing - Turn Signal Switch
« Reply #3 on: November 27, 2019, 03:17:10 PM »
I had this happen a few years back also. Check and make sure the brake light switch that is mounted at the top of the brake pedal is actuating when you push on the brake pedal. There are different brake light switches depending if the car has power brakes, no power brakes, what year. etc. If the switch is not correct for your car, the pedal may not travel enough to depress the plunger and actuate the switch to send power to the brake lights. Reach up under the dash with a screw driver and try depressing the plunger on the switch and see if the brake lights come on. Good luck and let us know what fixes the problem.
Jeff

rmarble57

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Re: Brake Light Testing - Turn Signal Switch
« Reply #4 on: November 27, 2019, 03:36:41 PM »
Thanks for the advice from forum members.

As previously mentioned, the brake lights have functioned up until yesterday so I don't think that the switch is incorrect for the car. 

I had already unlatched the turn signal plug under the dash and checked for any pins that might have slipped backwards, and still no luck.

I wouldn't think that if the signals are working (bright part of the bulb) that it would be a bad ground in the trunk, but I'll have a look. 

Also, with neither of the brake lights working I'm going to be more inclined to think it is an overall power problem as opposed to 2 wires coming loose simultaneously.

I just checked and I DO have power to one side of the brake switch on the pedal and power to the other side when the pedal is depressed.  I also have determined that the same wire that has power in the harness that comes up to the turn signal switch has power up to the switch.  Without knowing which wire takes power out of the switch I can't confirm if the switch is bad or not.  I don't get power coming from any of the other wires coming off of the switch which makes me believe that the T/S switch is the issue.

Also, just to be clear, the taillights function just fine as well.   Just the brake lights are not working.

Thanks
« Last Edit: November 27, 2019, 05:02:52 PM by rmarble57 »

texas swede

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Re: Brake Light Testing - Turn Signal Switch
« Reply #5 on: November 27, 2019, 05:38:01 PM »
Every time I have experienced this on my 67, it has been the brake light switch,
Probably changed the switch 5 times over the 42 years of ownership.
Texas Swede

JD

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Re: Brake Light Testing - Turn Signal Switch
« Reply #6 on: November 28, 2019, 12:25:19 AM »
Every time I have experienced this on my 67, it has been the brake light switch,
Probably changed the switch 5 times over the 42 years of ownership.
Texas Swede

^^^ Me too, started carrying an extra in the glove box.
'67 Shelby Headlight Bucket Grommets http://www.saacforum.com/index.php?topic=254.0
'67 Shelby Lower Grille Edge Protective Strip http://www.saacforum.com/index.php?topic=1237.0

rmarble57

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Re: Brake Light Testing - Turn Signal Switch
« Reply #7 on: December 06, 2019, 06:48:02 PM »
Alright, so circling around with the solution to my problem in the interest of passing along for others.

The issue was that:
I had turn signals front and rear
But I had no brake lights.
Hazard flashers would blink the fronts, but not the rear.

Checked the brake switch at the pedal.  Power on one side of the switch, power on the other side when pedal is depressed.

Issue turned out to be the reproduction turn signal switch. 
I purchased an NOS C7 switch, installed it, and as if by magic everything works.

Conclusion:  Shelby's have 6 lights in the back and 2 in the front.   Maybe too much amperage draw with all those bulbs through the reproduction wiring.

Thoughts?

JWH

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Re: Brake Light Testing - Turn Signal Switch
« Reply #8 on: December 07, 2019, 10:11:00 AM »
Thanks for posting what fixed the problem. Knowing what the "fix" is will be very helpful down the road when someone runs into the same issue. I am happy to hear you got it sorted out and working again.

Shelby_r_b

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Re: Brake Light Testing - Turn Signal Switch
« Reply #9 on: December 07, 2019, 10:22:42 AM »
Glad you got this fixed. Iíve lost count of the number of bad repop turn signal switched Iíve received in the past. And, it still amazes me how much can be affected by that one single component!
Nothing beats a classic!

Cobrask8

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Re: Brake Light Testing - Turn Signal Switch
« Reply #10 on: December 07, 2019, 02:31:47 PM »
I was going to say TS switch.

Very common problem on 67-70 Shelby's, as the addition of the extra bulbs does create the extra current draw and opens up the contacts.

Accurate fix.

1967 eight barrel

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Re: Brake Light Testing - Turn Signal Switch
« Reply #11 on: December 08, 2019, 01:20:47 PM »
Brake lamp switch, proper order with insulators and washers. The
 lamps also function through the headlamp/ turn signal switch.