Break lights
Thread Starter
|
Mountain Pass
Joined: Dec 2024
Posts: 134
Likes: 6
Break lights
Hey guys, 67 f100. I’m trying to figure out my break lights. I get good constant power to the driver side break light, and sometimes to the passenger side as well. This sometimes no. Anyone can point me to where the split happens as I think it is probably the problematic point
thanks
thanks
Tuned
Joined: Jun 2013
Posts: 308
Likes: 39
From: Homer, NY
The junction for the passenger side light is behind the driver's side light. From there, it goes down, behind the bumper, catches the liscence plate lights, across and up to the passenger side. Each has its own ground so check those too.
FTE Legend
Joined: Nov 2015
Posts: 30,935
Likes: 4,123
From: Angier, NC
You then have a taillight harness that plugs into the frame rail harness and runs across the rear from left to right and has plugs at each taillight.
As said each light has a plug that plugs into the taillight harness and a ground at each light. I dont know if your taillight housings are metal and if they ground to the bed body or if there is a ground wire from the housing to a screw on the bed body like my 81's but the picture looks the same.
Always start with grounds at the lights and new bulbs.
Dave ----
Thread Starter
|
Mountain Pass
Joined: Dec 2024
Posts: 134
Likes: 6
From the picture above and on my 81 F100's you have a harness that runs down the frame rail front to rear ending at the left rear frame end with a plug.
You then have a taillight harness that plugs into the frame rail harness and runs across the rear from left to right and has plugs at each taillight.
As said each light has a plug that plugs into the taillight harness and a ground at each light. I dont know if your taillight housings are metal and if they ground to the bed body or if there is a ground wire from the housing to a screw on the bed body like my 81's but the picture looks the same.
Always start with grounds at the lights and new bulbs.
Dave ----
You then have a taillight harness that plugs into the frame rail harness and runs across the rear from left to right and has plugs at each taillight.
As said each light has a plug that plugs into the taillight harness and a ground at each light. I dont know if your taillight housings are metal and if they ground to the bed body or if there is a ground wire from the housing to a screw on the bed body like my 81's but the picture looks the same.
Always start with grounds at the lights and new bulbs.
Dave ----
I do have blinkers and taillights
Trending Topics
Tuned
Joined: Jun 2013
Posts: 308
Likes: 39
From: Homer, NY
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
Hotshot
Joined: Oct 2009
Posts: 16,188
Likes: 4,792
From: Burbank, WA
Turn signals and brake lights work on the same circuit. If you have turn signals but not brake lights, you probably have a bad turn signal switch. In your words, that's where the split happens, and is often the problematic point.
Thread Starter
|
Mountain Pass
Joined: Dec 2024
Posts: 134
Likes: 6
As you say the turn signals and taillights all works well. The break light are not. You mean the break light switch is bad?
Tuned
Joined: Jul 2015
Posts: 290
Likes: 92
I believe what 52 merc is saying is, the brake light signal travels from the brake switch, up through the turn signal switch and then to the lights. This allows the turn signal to work even when the brakes are applied. If no turn signal is on, both right and left brake lights go on. When the turn signal is turned on, it breaks the voltage from the brake light switch and sends voltage from the flasher to the proper turn signal light.
Thread Starter
|
Mountain Pass
Joined: Dec 2024
Posts: 134
Likes: 6
I believe what 52 merc is saying is, the brake light signal travels from the brake switch, up through the turn signal switch and then to the lights. This allows the turn signal to work even when the brakes are applied. If no turn signal is on, both right and left brake lights go on. When the turn signal is turned on, it breaks the voltage from the brake light switch and sends voltage from the flasher to the proper turn signal light.
Tuned
Joined: Jul 2015
Posts: 290
Likes: 92
Take a look at this schematic. You see the Mech. Stoplamp Switch just below the fuse block? Wires 284 and 810 are attached to it. Wire 284 supplies power to that switch and when closed (brakes pushed) it sends that power out wire 810. Wire 810 then goes to plug M which then connects to the turn signal switch in your steering column. This switch allows brake light power to continue to the taillight that is not being used for a turn signal. That switch, in turn, will allow the flashing power to go to the other taillight so you get a flashing light opposite of your brake light. When no turn signal is used, wire 810 feeds both taillights through the turn signal switch. When this switch fails, it can cause all kinds of random taillight issues. The switch is relatively cheap and if the original one is in a truck and shows no problems, I'd replace it anyway. It will fail.
Thread
Thread Starter
Forum
Replies
Last Post
Steven_tx
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
1
Aug 1, 2009 08:27 PM