Weird Tail light issue...
Thread Starter
|
Freshman User
Joined: Aug 2016
Posts: 31
Likes: 0
Weird Tail light issue...
Alright here's my phenomenon. I have a 2001 f250 7.3 ext cab long bed 4x4 with a flat bed on it. I actually have 2 issues. I hooked up to my father n laws gooseneck trailer to pull a tractor. I noticed right after I unhooked that when I have my running lights on and step on the brake pedal my drivers side brake light comes on and my passenger side running light goes off and no light at all comes on on that side. Any one heard of this? Any way to trouble shoot this? Thanks!
Thread Starter
|
Freshman User
Joined: Aug 2016
Posts: 31
Likes: 0
On my flat bed I have two lights either side. one that is a reverse light only and is a clear lens and one that is a red lens and performs my turn signal, running and brake light function. they are the generic oval non led lights you can get about anywhere. they both have a ground coming out of them and I have them both grounded on the same bolt in the back of my flatbed. I have also noticed that on the same side I am having the issue with than when I turn that side signal on both the front and back signal flashes really fast.
Thread Starter
|
Freshman User
Joined: Aug 2016
Posts: 31
Likes: 0
Walleye, do you think I would be better off grounding each light separately? cangim with out my running lights on I still do not have a brake light on that side. I assumed those little oval lights were all one bulb. they are sealed anyway and I cant get inside of them to see. they around only a few months old.
Thread Starter
|
Freshman User
Joined: Aug 2016
Posts: 31
Likes: 0
When I took my box bed off to put my hay bed on it was a pretty simple deal (or so I thought) I unplugged my trailer wiring harness and then mounted it on my flat bed and plugged it back in. and then when right off my original harness to these lights. everything worked great.
Hotshot
Joined: Mar 2014
Posts: 10,750
Likes: 1,065
From: Douglassville, PA
Trending Topics
Postmaster
Joined: Nov 2003
Posts: 3,595
Likes: 0
From: Utah County, UT
So should be three wire plug then. Sounds like the bulb is out. You can ohm the brake wire see if there is any continuity. Then it will decide lamp housing vs wiring. Fast flash is similar to switching to leds, low current draw, burnt tail light would result in a lower draw.
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
More Turbo
Joined: May 2016
Posts: 717
Likes: 9
Attached are the Wiring Diagrams for your vehicle (Rear Lighting). Begin by identifying Connectors. Then determine if the Circuits are Open/Closed. Check Ground Circuits for continuity to a KNOWN good ground such as a Frame Bolt.
Electrical problems often take a good amount of time to troubleshoot. But, repairs are usually a few minute fix.
Good Luck!
Electrical problems often take a good amount of time to troubleshoot. But, repairs are usually a few minute fix.
Good Luck!
Thread Starter
|
Freshman User
Joined: Aug 2016
Posts: 31
Likes: 0
awesome thanks for the help guys, I will re-rout grounds and start over. I basically had grounds ruled out but I will revisit that. I assumed the bulb was still good because it would still light up for the turn signal and the running light. It blows my mind why if both running lights are on and I step on the brake the running light would go off and nothing would be on on that side??? I guess grounds do funny things......here is the funny thing. When I hook up to my gooseneck trailer my signal stops flashing fast and flashes normal? that because my trailer is grounded well? My brake light issue transfer back and does the same thing on my trailer though....
Cross-Country
Joined: May 2016
Posts: 66
Likes: 28
From: Southern California
The bright filament draws a lot more current than the dim filament. The bright filament can easily conduct the current for the dim filament through itself into it's power wire. When the tail lights are on, power comes into the dim filament, can't get to ground, so it goes into the bright filament out the other wire across to the opposite brake light, through its filament to ground. So the tail light works with no ground at the RH light with the brake lights off.
Now. When you step on the brake, there is power introduced to the bright filament on its wire, but it can't get to ground, so it doesn't light. The tail light now has +12V on both sides of its filament so it goes out.
You have a bad ground on the RH light. Could be the connector on the back of the "oval" light. Spread the pins out a little, or smoosh the female connector in the plug a little for a better connection.
Elder User
Joined: Sep 2011
Posts: 979
Likes: 4
From: Vancouver
I agree. Remove ground connection, sand rust/paint to clean steel, clean terminal, add some grease, use new bolt, washer, lock washer. Look at terminal for wire corrosion inside connector. I have had to re-tap the bolt hole to clean out the rust.
Posting Guru
Joined: Oct 2012
Posts: 1,910
Likes: 2
From: Hat Creek Ca
Just spit-balling here. Had a similar isue years ago and it turned out to be a bad turn signal switch. When you have one bulb doing different functions they are switched through the turn signals. When the contacts in the swich fail or break all kinds of wierd stuff happens.
Thread
Thread Starter
Forum
Replies
Last Post
Tonto Kowalski
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
33
May 10, 2018 03:29 PM
furyus
1948 - 1956 F1, F100 & Larger F-Series Trucks
2
Oct 20, 2009 12:07 AM
shane43028
1973 - 1979 F-100 & Larger F-Series Trucks
7
Aug 20, 2003 10:15 PM