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No brake light

Tiny
ERIC MCLEOD
  • MEMBER
  • 2008 FORD F-150
  • 5.4L
  • V8
  • 4WD
  • AUTOMATIC
  • 143,000 MILES
Been dealing with this for some time now. Brake lights were working at one time, now only the markers work, but no brake lights. No reverse light either. Turn signals and brake lights are on the same bulb. Someone told me once, I need to check a relay in the fuse panel. Turn signals do work though. Any ideas?
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Sunday, February 16th, 2020 AT 3:31 PM

29 Replies

Tiny
SCGRANTURISMO
  • MECHANIC
  • 4,897 POSTS
Hello,

This sounds like you have got a problem with Ground 303, which is located on the left hand A pillar. In the diagrams down below I have included the backup and exterior lighting diagrams for your vehicle as well as the location of Ground 303 for you. Please inspect the ground and make sure that it is clean, tight, corrosion free, and making good metal to metal contact, and get back to us with what you find out.

Thanks,
Alex
2CarPros
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Sunday, February 16th, 2020 AT 3:51 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good evening,

You will need to test for power in and out of the brake light switch. From there, it goes to the turn signal switch and then to the bulbs.

You will need a test light or voltmeter to do the testing.

https://www.2carpros.com/articles/how-to-check-wiring

Roy
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Sunday, February 16th, 2020 AT 3:53 PM
Tiny
ERIC MCLEOD
  • MEMBER
  • 21 POSTS
Thanks for the quick response. Anything on the reverse light not coming on? Seemed a few weeks ago everything was working just fine.
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Sunday, February 16th, 2020 AT 4:03 PM
Tiny
ASEMASTER6371
  • MECHANIC
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Back up circuit attached. Check the fuse listed for power on both sides.

Roy
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Sunday, February 16th, 2020 AT 4:11 PM
Tiny
ERIC MCLEOD
  • MEMBER
  • 21 POSTS
Had someone come look at the lights. Used a volt meter and it said there was only 7.7 volts going to the taillights. I'm going to pick up a new brake light switch tomorrow and have him put it in for me. Still haven't looked at the reverse light though. One thing at a time.
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Monday, February 17th, 2020 AT 5:25 PM
Tiny
ASEMASTER6371
  • MECHANIC
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Keep us updated.

Roy
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Monday, February 17th, 2020 AT 5:47 PM
Tiny
ERIC MCLEOD
  • MEMBER
  • 21 POSTS
Okay, not sure of this has anything remotely to do with my issue. The guy I had come to me just messaged me and mentioned he did some digging and said he thinks my issue could be caused by a combination switch for the turn signal. Those actually work, the brake lights don't work. Thinking I need to drop it off someplace more legit and see if they can dig into it. Thoughts?
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Tuesday, February 18th, 2020 AT 10:29 AM
Tiny
ERIC MCLEOD
  • MEMBER
  • 21 POSTS
Also my third brake light seems to be the only one working. Forgot to mention that.
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Tuesday, February 18th, 2020 AT 10:30 AM
Tiny
ASEMASTER6371
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You need to test for voltage from the switch to the turn signal switch in the diagram that Alex and I posted.

If you have power to the switch, then yes, you have a bad multifunction switch.

Roy
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Tuesday, February 18th, 2020 AT 10:38 AM
Tiny
ERIC MCLEOD
  • MEMBER
  • 21 POSTS
The voltage was about 7.7 at the plug. This would keep the brake lights from working?
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Tuesday, February 18th, 2020 AT 10:44 AM
Tiny
ERIC MCLEOD
  • MEMBER
  • 21 POSTS
And when using my 4-ways all but one works.
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Tuesday, February 18th, 2020 AT 10:45 AM
Tiny
ASEMASTER6371
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7.7 where?
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Tuesday, February 18th, 2020 AT 10:48 AM
Tiny
ERIC MCLEOD
  • MEMBER
  • 21 POSTS
At the rear light.
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Tuesday, February 18th, 2020 AT 10:49 AM
Tiny
ASEMASTER6371
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No, you need to do the testing I asked you to do at the switch and at the multi-function switch.

Do those tests first.

Roy
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Tuesday, February 18th, 2020 AT 10:54 AM
Tiny
ERIC MCLEOD
  • MEMBER
  • 21 POSTS
Crap! That's right.
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Tuesday, February 18th, 2020 AT 10:58 AM
Tiny
ASEMASTER6371
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Keep me updated.

Roy
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Tuesday, February 18th, 2020 AT 11:02 AM
Tiny
ERIC MCLEOD
  • MEMBER
  • 21 POSTS
Okay, final update on my issue: Tail lamp harness needs replaced. The volts shot up to 12-13 at the plug under the bed. Then back down to 7-9 when plugged back in. Only thing is, Ford discontinued the harness and there's none new to be found. Having to check salvage yards for one, can't be guaranteed they can pull it off without damaging. And I can't find videos on removal/replace of the harness.
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Monday, February 24th, 2020 AT 6:48 AM
Tiny
ASEMASTER6371
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You need to be careful about removing it. When you remove it, you will know what needs to be done to replace it. It is not that hard, just time-consuming.

Roy
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Monday, February 24th, 2020 AT 7:10 AM
Tiny
ERIC MCLEOD
  • MEMBER
  • 21 POSTS
Thanks so much for your guidance, Roy. I'll keep this site in my favorites for the future.
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Monday, February 24th, 2020 AT 7:16 AM
Tiny
ASEMASTER6371
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You are welcome.

Always glad to help.

Feel free to leave a review for us. We appreciate all the feedback.

Roy

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Monday, February 24th, 2020 AT 7:48 AM

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