Ok, so I installed this hopkins 7 way plug on my truck so I could pull around my enclosed trailer. Originally it had the 4 way plug. I am pretty confident I matched all the wires to eachother correctly when I spliced the 7 way onto the 4 way. But some crazy stuff is happening. When I engage the left turn signal, it works fine, on both the truck and trailer. When I engage the right turn signal, it works fine on the truck, but it sends signal to both trailer turn signals as if i had the hazards on. And when I turn the headlights on, only the right light on the trailer illuminates. Basically, all the lights function correctly on the truck, but not the trailer. The brake lights seem to be the only thing that works fine on the trailer. I checked all fuses on the truck, all was fine. And I know its an issue with the vehicle and not the trailer. Any help would be great!

 

Why did you go with a 7 pin those usually use trailer brakes?

 

Still sounds like an issue with the trailer to me. Do you have a test light or voltmeter ? If so you can verify the pins on the truck side. Only pin 6 should be pulsing when the right turn signal is on.

 

Which plug conversion did you use? I've used a couple that the 4 flat goes into the back via a plug then you wire the other three. It has two plugs on the trailer end/ A 4 flat and a 7 round. I've found this to be really handy. However, that isn't fixing your problem.

Let's track down where your issue is. Use a test light with a probe. With the truck by itself, is every prong working properly? Put the probe into the left turn and watch if it's flashing. If all the lights are working properly with the test light, then the problem may lie in your trailer connection. This can be either the plug itself or the wiring in it. Has the plug been dropped or allowed to lay in the dirt?

 

Need to check your wiring.


I second this, Really no need unless that's whats on the trailer. But if so it has electric brakes that are not working(no feed wire).

 

I bought the 7 way plug to replace the 4 way on my truck because I wanted electric brakes and because it’s impossible to pull an enclosed with a 4 way. The electric brakes and 12v accessory work fine. I will need to buy a probe for sure as I don’t have one yet. I tried a multimeter yesterday and didn’t get a reading from anything. Very confusing. The Hopkins that I bought had this weird plug look, not something that would fit into a 4 way. But it came with a wire diagram and I matched the wires accordingly. I have a new plug with a 4 way connection on order from Walmart.

 

You need a wire that comes off the brake switch for the trailer brakes so you can put a controller on it. With out one it will lock up the breaks. If your truck had the trailer package you would already have this. Since you don't you have to add it.

 

I have a curt brake controller set up. And it works great.

 

I had a thought. (Really!) Since you have a 7 prong connection now, you're going to need a 7 to 4 converter to pull a small trailer if you need one. Hook a pair of tow lights for a tow dolly into the 4 prong adaptor and see if they work. If they do, your trailer is the problem child. If they don't, it's in your wiring somewhere.

 

Even easier there are 7 pin to 4 pin adapters with built in LEDs for lights, left brake/turn and right brake/turn voltage. Still doesn't tell anything that a voltmeter or test light couldn't do.