I hooked my boat up to my 2001 f150 the other day to see if the wiring was ok on the trailer. I had a problem. After a couple of hours of hair pulling I figured out the problem was not in the trailer, but in the wiring on the truck. The wiring harness is ford.
Here is the problem; I have running light on both sides of the trailer. This means the brown wires is good. I have break lights on the right side of the trailer. Green is good. I have no turn/break lights on the left side. Yellow is bad. Will I need to repalce the whole system or can I get by with replacing the bad wire? Or is the problem more complicated than I think?

 

Did you check the left side brake/turn on the left side from the connector directly?

You should be able to stick your test light prop into the left side pin directly and when you hit the left turn signal, the test light should blink. That will determine if it's the trucks wiring or not.

Good luck!

Mitch

 

http://www.trailerwiring.com/cgi-bin...cgi?part=48675

Or get one of those to test.

 

I did test the plug directly. That is how I figured out it was the truck wiring and not the trailer. I actually started at the back of the trailer and started working my way up to the truck.

 

Ok. The wire harness has a connector up along the frame, right around the spare tire area (you will have to drop the spare). Up to this point, all F150's are wired exactly the same from the firewall to this point. The difference is the type of connector you get from the factory...... No tow package, you get the flat 4 connector. Tow package, you get the round 7 pin.

I'd disconnect the connector at that point and then test for the left brake/turn light. If it works there, then it's only the 7 pin harness. If it does not work to that point, then you have to move ahead. That's where it would get 'messy', as a lot of wiring will start to merge together at that point.....

Mitch

 

I do have the seven pin harness. I will look at it tonight and hope the problem is there! This gives me something to go on!

Thanks Mitch.

 

Mitch,

I did as you said, dropped the tire; found the connection and then got totally lost. I disconnected the connection and realized I didn't know what I was looking for exactly. I wasn't sure which connection I should be testing. I'm probably in over my head and will need to have someone else find the solution. Thanks for your advise, I do appreciate it.

Sherm65

 

You gotta find the wire you are looking for on that connector. You said it was the 'yellow' one from the 7 pin. Find where that wire goes to the harness connector (by the spare). Match it up to the same pin hole that goes to the connector that goes to the front of the truck. Stick your test light prop into that pin (and ground the test light) and activate the turn signal. Your test light should be blinking.

If it's not, then test it on the other turn signal pin. If that one blinks, then you have found the problem.... Well, you know it's not the 7 pin harness. You will now have to move forward, following the wire and trace it to it's next connection point towrds the front of the truck.

If it DOES work at the pin, then the problem IS with your 7 pin connector. Might just be a bad connection. By removing it and putting it back on, might be enough to get continuity again......

Good luck!

Mitch

 

Mitch,

This weekend was the first real chance I had to follow your advise. I was able to trace the problem all the way back to the fuse box. I did not know that there are more than one fuse to run the tow package. In fact there are three. I had to replace two fuses and that solved to problem.

Thank you for your advice and help.

Sherm65

 

Now that's really odd..... I thought the fuse for the brake light/turn signals would have been for both sides.... I guess that's why I didn't think about the fuses being an issue???

Good job and glad you were able to resolve it!!

That helps me out too..... Now I know to check those fuses, no matter what!!

Mitch

 

I had this exact same problem about a month ago: One side worked good, but the other didnt' work at all. I, just like you, assumed that 1 fuse would handle both sides. I just about pulled all my hair out trying to locate the problem. I literally spent upwards of 6-8 hours looking for it. When I was just about to start abusing my truck/trailer, I decided to take a peek at the fuses. Low and behold, seperate fuses. I felt SO dumb This is the 1st time I've actually admitted that the problem was simply a fuse. My wife still thinks I, being a mechanical genuis, had to re-wire the whole truck