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Brake lights stay on?

Tiny
MANUEL12344
  • MEMBER
  • 2003 NISSAN SENTRA
  • AUTOMATIC
  • 205,000 MILES
A couple of days ago I notice the top brake light staying on while not pressing the brakes only with the headlights on. When they off all the brake lights work fine. Also the two bottom brake lights go off when I hit the brakes. I replaced the battery ground cable that was broken and a few months ago and the brake switch. Before I notice the top brake light staying on and acting like one of the bottom ones I already had one on the bottom brake lights going off when hitting the brakes while headlights are on. Please help. I have also check all the fuses, I have follow all the wiring from the trunk to the fuse box and everything seems fine.
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Thursday, November 19th, 2020 AT 5:34 PM

11 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

This is going to take a few tries. If you look at the attached pic below, I circled the wires that are near the high mount brake light which will have constant power when the headlamps are turned on.

Let me know if the 3rd brake light comes on with both the headlamps and the parking lamps. Next, for that light to come on with the headlights, there has to be a short to power in one of the tail light/parking lights wiring. Follow the red/green wire back from the light itself and see if you can find anywhere it is damaged and shorted. The red/green wire to the third brake light isn't too long. It will tie into the brake light wiring in the rear of the vehicle.

Let me know what you find.

Joe
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Thursday, November 19th, 2020 AT 5:56 PM
Tiny
MANUEL12344
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  • 7 POSTS
Yes, the 3rd light stays on with parking and headlights and I actually just double checked and follow the wiring from brake lights socket to 3rd light and everything seems fine with the wires. It is very weird because I think the ground cable was half broken and I had the problem with the one brake light but it broke completely and then the 3rd like problem came up. Now that is replaced I am not sure was it happening a short a ground problem, so confused.

It has to be a short or something because the tail lights are less bright than they usually are, but if wiring is fine what else can cause this short? I’m also replacing this socket tomorrow it seems to make contact but just looks a little like melted. I don’t know if the can cause this I did attach a picture of it.
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Thursday, November 19th, 2020 AT 6:33 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

I see the pin on the left looks like it is lower. What ground wire was bad? If you have a bad ground, it is possible that power is back feeding through the third brake light and turning it on. Also, a weak ground will cause the lights to be dimmer than normal.

Let me know.
Joe
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Thursday, November 19th, 2020 AT 6:59 PM
Tiny
MANUEL12344
  • MEMBER
  • 7 POSTS
Battery ground wire I replaced with a 4 gauge one, but looking at the original one it has like 2 parts like it screws to the chassis twice. The one I got just one time at the end not sure if that makes a difference. Lights are a lot dimmer and yes most likely a ground problem, just not sure what ground wire I should be looking at now.
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Thursday, November 19th, 2020 AT 7:01 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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The cable you have looks like the connector went to the body and the opposite end without the connector likely went to the engine. Where did you attach the new one?
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Thursday, November 19th, 2020 AT 7:39 PM
Tiny
MANUEL12344
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  • 7 POSTS
Yes, the original one was attached to the body and the other end which it broke was attached to engine or transmission. The new one I attach it to engine or transmission not the body.
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Thursday, November 19th, 2020 AT 7:44 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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On the inner fender? Do me a favor. Try running a separate ground to the third brake light to see if it changes things.

Joe
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Thursday, November 19th, 2020 AT 7:47 PM
Tiny
MANUEL12344
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  • 7 POSTS
I’m sorry Joe, but can you guide me a little on how I can run a separate ground for that light?
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Thursday, November 19th, 2020 AT 7:56 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

Absolutely. At the light socket, simply splice a wire to the black wire which is the vehicle's ground, and place the opposite side on a known good ground. Heck, if you have a long enough wire, run it back to the battery ground. Or, simply find a good solid ground somewhere in the body.

Let me know if that makes sense.

Take care,
Joe
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Thursday, November 19th, 2020 AT 8:06 PM
Tiny
MANUEL12344
  • MEMBER
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All right Joe, thanks for your patience. So I splice a wire from the third light to the battery ground also tried it with just body ground and nothing happened. So look I don’t know if what I did is okay or not but with that same wire I spliced I started touching the other brake lights and notice that if that wire makes contact with bulb it does something different so I went ahead and splice a extra wire and attach one to each brake bulb and crazy enough the problem is completely gone I did blow out the fuse for the parking, tail and license plate lights wire figuring out how to wire it but I replaced the fuse and it works perfect, might be temporary but is just what I need to get back in the road tonight and deliver so I will let you how it goes went I get back tonight. Joe thank you so much for all your help and time. You been doing this for over 12 years, helping people and that is amazing from you. Thank you.
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Friday, November 20th, 2020 AT 2:02 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

You got it! It is a ground related issue. Power is back feeding into the third brake light. If it is working, simply make your fix permanent.

You are very welcome. I'm just glad I was able to help. Please feel free to come back anytime in the future if you have questions or need help. You're always welcome here.

Take care,
Joe
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Friday, November 20th, 2020 AT 8:52 PM

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