Left brake light problems
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Junior User
Joined: May 2002
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From: Oceanside USA
Left brake light problems
I've got a 70 F250 w/ left brake light not working. I have replaced the brake light switch and bulbs and no luck. I swapped light housings it works on the right side. There is no voltage coming from yellow and brown wires underneath the vehicle. I thought both brake lights shared the same signal. Any ideas?
Fleet Owner
Joined: Jun 1999
Posts: 24,552
Likes: 74
From: Creedmoor, North Carolina
Originally Posted by F250Dave
I've got a 70 F250 w/ left brake light not working. I have replaced the brake light switch and bulbs and no luck. I swapped light housings it works on the right side. There is no voltage coming from yellow and brown wires underneath the vehicle. I thought both brake lights shared the same signal. Any ideas?
I would start at the left bulb socket and start working forward. My suspicion is dirty wire connection, or chaffed wire grounding out. If the left front is blinking it is not the flasher.
One of those Icepick looking testers with the ground wire in the end of the handle and a bulb inside of it works really well with these issues.
G-luck
John
Senior User
Joined: Dec 2002
Posts: 473
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From: SW Florida
Since the brake lights and turn lights work off the same circuit, the brake lights are interrupted by the turn signal switch whenever the switch is on. If the switch is a little loose, this can cause the random brake light problems.
I'd definitely do the diagnosis of the rest of the truck first to make sure it isn't something else, but if you can't find any other problems I'd look at the switch.
I'd definitely do the diagnosis of the rest of the truck first to make sure it isn't something else, but if you can't find any other problems I'd look at the switch.
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Junior User
Joined: May 2002
Posts: 77
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From: Oceanside USA
Thanks for replies everyone. I did a visual on the harness from the rear to the inside the cab. Visually it looks good though will tracing the wires there are many areas I cannot see due to the fuel tank. From under the dash I loose track of the wires due to the maze of wires. So am I to understand the left brake and left turn wires run through the turn signal switch, from thinking about it that makes sense. And yes my left turn signal and turn signal are working. So the brake problem could be caused by a loose turn signal switch? Also I noticed a connector under the dash which I think goes to the rear, i will unplug and test voltage there first, if no voltage then it sound like the turn signal switch right?
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Fleet Owner
Joined: Jun 1999
Posts: 24,552
Likes: 74
From: Creedmoor, North Carolina
Dave, My suggestion is to start at the rear of the truck and work forward.
If the left front is flashing then the flasher should be ok.
With the left side flashing start checking the wire at the tail light with a tester and move forward until you find the pulse.
Bill may know which wire is which, but there are only three, green, yellow, and brown going to the rear. Eliminate two and you will have one to hunt.
John
If the left front is flashing then the flasher should be ok.
With the left side flashing start checking the wire at the tail light with a tester and move forward until you find the pulse.
Bill may know which wire is which, but there are only three, green, yellow, and brown going to the rear. Eliminate two and you will have one to hunt.
John
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