Discussions

Hi. My Chevy truck had 4 pin wiring added to it when the hitch was put on. I've removed all of the 4 pin wiring that was put on, including the electronic taillight converter. I've replaced it with a 7 pin connector. As far as I can tell, everything is correct. However, it obviously isn't because when I connect up to my trailer with 7 pin wiring, the brake lights on the trailer don't work. The running lights, hazard lights and signal lights are working correctly. What am I missing?  
 
Thanks

Check the fuses at the fuse box. On a ford it's under the hood. Easiest check to do before tracing and testing wires.

bmw8866 said "Check the fuses at the fuse box. On a ford it's under the hood. Easiest check to do before tracing and testing wires. "

Thanks, but the brake lights on the truck are working fine, so it can't be the fuses. It is only the trailer brake lights that aren't working.

In a truck, the brakes will likely have their own fuse, and it will be SPECIFICALLY a fuse for the trailer. Check to see if there is a secondary fuse box under your hood (likely at the back) and see if you have blown a fuse there.  
 
Otherwise, I would troubleshoot by comparing what is happening "electrically" between the 4-pin original setup and the 7-pin current configurations, that which you have changed. If you had a 4 pin, it was likely installed after original purchase, no? What was different, or is it that your 7-pin was factory wiring that you are now trying to figure out? A 4-pin config has 1 wire for running lights (doubled over for brakes), left turn, right turn, and ground. The new 7 pin likely has the brake lights as a separate circuit, the trailer brake actuator as a separate circuit, and backup as a separate circuit (tied into back up lights) which take up the other 3 wires (7 vs 4) ... so figure it out from there ...  
 
 
 
If you have no brake lights, its likely because they come in on their own circuit which, if it's a truck, is likely fused under the hood in a fuse box.  
 

My Chevy was bad for blowing the trailer brake fuse, it is under the hood on the driver's side. When this fuse blows your truck brake lights work but your trailer brake lights don't

That the trailer brake fuse is ok. I don't think that circuit is used. When the hitch was put on, the buy used quick connects and scabbed onto the existing brake/signal/taillight wires at the back of the truck. As I think about it, the wires for the left and right turn signals are just for turn signals. There is no power for brakes going to those terminals on the 7 pin plug. So, do I just split the brake wire onto the left and right turn wires, or do I need something to split it for me? I did remove a converter that was put on for the 4 pin wiring.

If your truck uses separate bulbs for brake lights & signal lites you will have to reinstall the converter. The 7 pin connector will not separate the two. The brake terminal on the plug is for electric brakes.

Good day,  
 
I', having the same issue, and it isn't something specifically "wrong" with any of the wiring, just a conflict. I'm borrowing a trailer from a friend, which is wired specifically to his Chevy, while my truck is a Ford. The issue for me is that his 7 pin is wired for a different configuration with respect to the trailer brakes pin. This causes a virtual "short" on my truck. Once I disconnected the brake controller from inside the cab of my truck, all the lights work perfectly.  
 
There are unfortunately multiple wiring standards for trailer lighting, the challenge is figuring out which one you are running. You can Google this topic and get many results.  
 
Good luck.

I'll try reconnecting the converter again. I'm soldering all the connections so that should not be a problem in the future with poor connections there.

Get PA LED 7-way tester, SKU: 8271173.  
 
 
It will tell you in a flash whether the fault is with the truck wiring, or the trailer.  
 
It's on sale for five bucks until Sunday.

I reinstalled the converter and had the truck all wired up correctly. I got the tester from PA and it tested fine for the turn signals, clearance/marker and brake lights, which were the only things wired.  
 
I connected the truck up to my car hauler (wiring only, not hitched through the ball) with factory 7 pin and it all worked as it is supposed to work.  
 
I added a 7 pin connector to my boat trailer, leaving the 4 pin as well. I connected up (wiring only, not hitched through the ball) to the trailer. Signal lights worked, brake lights worked, and only part of the clearance/marker lights worked. The rear clearance lights did not work, only the ones around the wheels.  
 
From the wiring on the boat trailer (all connections soldered):  
Yellow/white and green/white to white (ground)  
Yellow to yellow (left turn)  
Green to green (right turn)  
Yellow/brown and green/brown to brown (clearance/marker lights).  
 
The 4 pin connection on the boat worked fine (other than blowing fuses when the trailer was wet).  
 
Any suggestions as to why all of the clearance lights aren't working?]  
 
Thanks again.

ZachT said "I reinstalled the converter and had the truck all wired up correctly. I got the tester from PA and it tested fine for the turn signals, clearance/marker and brake lights, which were the only things wired.     I connected the truck up to my car hauler (wiring only, not hitched through the ball) with factory 7 pin and it all worked as it is supposed to work.     I added a 7 pin connector to my boat trailer, leaving the 4 pin as well. I connected up (wiring only, not hitched through the ball) to the trailer. Signal lights worked, brake lights worked, and only part of the clearance/marker lights worked. The rear clearance lights did not work, only the ones around the wheels.     From the wiring on the boat trailer (all connections soldered):   Yellow/white and green/white to white (ground)   Yellow to yellow (left turn)   Green to green (right turn)   Yellow/brown and green/brown to brown (clearance/marker lights).     The 4 pin connection on the boat worked fine (other than blowing fuses when the trailer was wet).     Any suggestions as to why all of the clearance lights aren't working?]     Thanks again. "

Zach you salty dog...stop rewiring things and get yourself a converter that will allow you to plug any 4 pin into your now properly wired RV connector on your truck.  
 
and consider investing in submersible, waterproof boat trailer lights.

If the lights are working as you say on the boat trailer, then there has to be a problem on the trailer now. It appears you have the truck wired properly now and there is just a problem with the trailer. Your rear park lights on the trailer should come on with any clearance lights. They work on the same circuit for the trailer. So if some work and others don't, its a problem on that trailer....You can just have a 7 pin connector on your vehicle. If you have to pull something with a 4 pin, there is an adapter you can buy to plug into your 7 pin on the vehicle. This is providing you have wired it according to the proper positions they should be on your 7 pin on the truck. .....I always disconnect the trailer plug when backing up into the water. It just eliminates any headaches.

 
 
Edited by TR7, 2017-08-22 23:03:21

cotr said "My Chevy was bad for blowing the trailer brake fuse, it is under the hood on the driver's side. When this fuse blows your truck brake lights work but your trailer brake lights don't "

On a 7 pin connector, the brake circuit marked is for the actual trailer brakes, not the brake lights. If your lights on your vehicle are separate brake and turn signal lights, then they are always converted so as to be the same circuit on the trailer exactly as an older vehicle would be. Your signal lights on the trailer is also your brake light circuit. Just so there is no confusion from the video you showed.  
 
Edited by TR7, 2017-08-22 23:07:50