Hello,

I have a 1995 Ford F150 XLT. I have replaced the existing "crimp on" type 7 pin trailer plug with a "T-Connect" connector 4-pin. I then took this 4-pin and connected it to a 7-pin (made to do so by the same company), and inserted one of those 7-pn test modules with the lights on it to test it.

Every light on the truck works GREAT!

On the connector I get headlights, turn signals and brake lights. So far so good. When I turn on the headlights, the turn signals each work. Then I hit the brakes, and they don't work, but they do on the truck, just not working on the connector.

If, at this point (lights on, brakes on) I turn on either turn signal, I get brake lights, one steady, the other blinking (approprate since I am using the turn signal). With the truck off (turn signals won't work this way), headlights on, brakes on, still no lights at the trailer harness for the brakes, BUT if I turn on either turn signal, the brake lights come on (of course no turn signals because the truck is off).

I tried independantly grounding the white wire to the frame, no change. I thought possibly that I had a bad light ground, so I took the lights out, found the ground wires, hitched them together and connected that to a frame ground, with no change.

Any ideas?

Thanks!

Mike

 

I'm having a hard time understanding what you did exactly. Did you change the plug on your trailer to 4 pin or the socket on your truck to 4 pin?

I think you just have some wires crossed. Go back through and check the pin outs for the connectors.

Last time I wired up trailer lights I had my girlfriend helping me. When I flipped the turn signals on and asked her if they worked she said "they're working...oh, now they're not...now they're wor...nope not working...working...not working...working...not working"

Man I miss her

 

RocketScott,

This is the truck side wiring, with a dummy test plug inserted (has lights on it to tell you what's working, and what's not).

There's no way to mis-wire this thing. You unplug the stock wiring connector about mid-bed under the truck, and plug this T adapter into it (with the 4-pin socket on it). That's all there is supposed to be to it.

Once you put in the "T" you have a 4-wire "ready to go" connector. That connector can then be attached right to a trailer, or to a 7-pin round type connector (which I did and mounted to the truck). Of course you have to wire the trailer brake controller (which I don't have) to it seperately, but it sure beats using crimp on connectors and having then corrode in the future.

Mike

 

Ah, OK. I had to reread it a few times to understand what is going on.

If the ground was bad nothing would work, they all share the same ground. The trailer lights have two filaments that have to share duties as tail, brake, and turn lights same as the truck. If there is no way to miswire those connectors assuming the plug is right for your vehicle and there is no way to miswire the 4 to 7 pin connector all I can think of is the test plug.
I have never used a test plug to test the trailer wiring so I don't know how they work or how to read them. I have a set of stand alone trailer lights that I switch between cargo trailer and boat trailer. I plug those in and put them where I can see them to test everything.


Have you tried plugging into actual trailer lights to see what it does?

 

I've had those testers go bad and have the wrong led's light up when actually they are working properly. Do you have a trailer you can test it on.

 

The issue, found once connected to different trailers, was that the 4 pin to 7 pin connector was bad, although it was brand new out of the box.

The 4-pin T connector however was good.