# Brake Light Electrical Issues



## jtwoods4 (Dec 22, 2011)

69 GTO.... 

Brake lights work fine with headlights off. 

When I turn on the headlights the rear lights light up fine. 

When I apply the brakes with the headlights on the drivers side brake light does not light up.

What is going on?


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## ALKYGTO (Mar 29, 2010)

I'd start with the basics JT and check all the grounds for the tail lights. They can be head scratchers for sure but good grounds are critical to proper operations. And when i say check them I mean disconnect each one and make sure it is contacting bare metal. Good luck.


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## SANDU002 (Oct 13, 2004)

Make sure all the contacts are clean by hitting them with a little 1000 grit metal sandpaper. You may also then notice your lighting is brighter too.


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## jtwoods4 (Dec 22, 2011)

Last night I replaced one of the Brake Light sockets that was questionable. Did not fix. I will disconnect each ground and sand the contact point this weekend.

If that doesn't work I have looked at the wiring diagram and traced the rear harness up to the steering column connector. I guess that connector is the next place to check in the signal chain.


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## geeteeohguy (Feb 2, 2008)

The 'horseshoe' connector can and does give fits every once in awhile. My '65 had no brake lights when the turn signal was on. Turned out to be the connection in the horseshoe connector under the column. It was the last or next to the last wire on the very edge of the thing. Over time, connections loosen and get cruddy. Mine had simply backed out. The rear tail lamps on these cars use the socket-to-body contact for a ground. This can often give you problems. One sure fire fix is to install a 3-wire socket, where the third wire can be grounded with a bolt.


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## GoatGuru (Oct 1, 2013)

jtwoods4 said:


> Last night I replaced one of the Brake Light sockets that was questionable. Did not fix. I will disconnect each ground and sand the contact point this weekend.
> 
> If that doesn't work I have looked at the wiring diagram and traced the rear harness up to the steering column connector. I guess that connector is the next place to check in the signal chain.


remove all grounds and clean grounded area use electrode grease very little will help connection on bulbs, and do not use on grounded area. other thing is dbl check for a crossed wire or a grounded one that shouldn't be a ground. other wise get a wiring Diagram and chase the wires one by one. with a amp meter .. you will be able to see the draw on the meter to narrow it down. and clean every thing you get dirty when your old..LOL if you need a electric Diagram for your car give me a PM and year of car and ill send one to you free... because that's the way I roll.. Travis 

AND geeteeoguy is correct socket to body for a ground is not fun YUP I did the same on my 68 3 wire socket fixed it because 68 rear taillight housing are fiberglass. not a good ground I replaced my front turn signals the same way And check the connection in the column turn signal


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