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Old 10-08-2021, 01:29 PM   #1
72bigred
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Brake and tail light issue

Brake lights work, running lights work..

With running lights on if ya hit the brakes the right light goes totally out. Grounds all clean, no noticeable wiring issues upon inspection.. it has to be something simple figured so.eone may have seen this before.

Thanks
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Old 10-08-2021, 03:20 PM   #2
67C10Step
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Re: Brake and tail light issue

Hate to say it, but almost every time I've seen running lights go out when the brakes are applied it has been a grounding issue. Try running a designated ground wire from the light that is going out to a known ground. If that clears the issue you know it's a ground problem.

Other than ground, the two circuits should not have much to do with one another. The only other place might be the directional signal switch.

Someone else will be along with probably the exact fix.
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Old 10-09-2021, 10:35 AM   #3
72bigred
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Re: Brake and tail light issue

I totally agree on the grounding aspect, probably 90% or better that has been the issue. This round I took every step to avoid it. Going to replace the light switch as that is my only avenue at this point.
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Old 10-09-2021, 10:56 AM   #4
Getter-Done
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Re: Brake and tail light issue

Here is a good Stock ground strap location thread.

Link:https://67-72chevytrucks.com/vboard/...strap+location

This is 67/72 truck , but exact locations are not critical.

Just as long as they are there

You may allready have all these in place.

Hope this helps.
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Old 10-09-2021, 11:55 PM   #5
RustyPile
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Re: Brake and tail light issue

Quote:
Originally Posted by 72bigred View Post
I totally agree on the grounding aspect, probably 90% or better that has been the issue. This round I took every step to avoid it. Going to replace the light switch as that is my only avenue at this point.
Guaranteed that will not fix the problem.. Yours is 99.997% a ground problem.. Remember, the bulb socket has to make good electrical contact with the light housing and the housing has to make good electrical contact with the fender or bumper where it's mounted.. All the contact points for everything has to have good electrical contact back to the battery negative post..

I have extensive automotive electrical experience so all this is basic to me.. I had grounding issues on my truck with the running/turn signals.. After good trouble shooting techniques, I determined that both front bulb sockets didn't make good contact with the light housings.. The sockets are just crimped to the housings and had become loose.. I tightened the crimp and then cleaned the contact areas on the housings and sockets.. Using a 250 watt soldering gun, I flowed a good "solder bridge" across the crimps.. 4 years ago and the lights still work as they should..
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