I have a 1998 F150 and have lost power on both right and left brake and signal lights on my trailer plug. Does anyone have any suggestion where I might start looking for the problem?

 

First, check the fuses under the hood on the drivers side. If you have a 12v test light (looks like a screwdriver, with a light on the end and a ground wire coming out of it), check the connections at the plug. If they work, it's the trailers lights. Could be anything at that point.

If you have good fuses, but no power at the plug, could be a loose connection on the wiring harness. Make sure it's tight.

Since it's both the brake and signal lights, my guess would be the fuses.......

Good luck.

 

Mitch is right that you should check the fuses. If you don't have any luck there are a few other things you can check. The harness for the trailer wires runs along the driver's side frame. A few feet in front of the rear bumper there is a connection in the harness for changing the 4-pin to a 6/7 pin connector for those folks who didn't get a factory tow package and want to upgrade. Check the connection for corrosion. Check your plug on the hitch and the trailer as well. The wires connected to the trailer plug can take a beating if you do a lot of backing etc. so see if you have a broken wire. The wires you want are the Yellow and the Green.

Not that you asked but...
4-Pin Connector
Brown=Tail Lights
Yellow=Left Turn
Green=Right Turn
White=Ground

Yellow and Green are energized at the same time for Brake lights

6-Pin Connector
Same as above +
Blue=Electric Trailer Brakes
Black=Aux 12V power (winch battery etc.)

7-Pin Connectors can be totally different, if you have one let me know.

Good Luck!

 

I'm trying right now to wire in a combination 7/4 plug connector. I've traced out the yellow, green, brown/white, and white wires for the standard 4 pin connector. I noticed on my harness there are 3 wires that do not continue beyond the connection behind the rear wheel well. A blue, orange, and black/green stripe wire. Any clues? What is my best approach to this conundrum?

 

88blkgtstang,

Oh, I think I see what you are doing now?? You must have an "off the shelf" 7/4 connector and you have to manually splice the wires, correct?? I replied to you in another post and assumed you were using the Ford connector, and you could just plug it into the harness and it's a done deal.....

Well, the blue wire is for the trailer brakes and you won't get any 12v out of it unless you have a brake controller hooked up. The only other wires that you would have for the 7 pin is the 12v charge line for the trailer battery and a backup light. The 12v charge and the backup light need to have the additional relays added to the box under the hood. Sounds like you already have the 30a fuse for the brakes, but you still need the controller for it to work.

Without the relays, you will not get any 12v to those other wires. The ignition needs to be on (or maybe even the engine) for the 12v charge one to work, even with the relay. The backup one would work once you put the truck in R of course (with the relay too). Sorry, I don't know what wire color is which for those last two....

good luck!

Mitch

 

Hi MitchF150,

I haven't checked the other post yet....

I found out that the black/green stripe wire is the reverse. I got 13.8V when I put the truck into reverse. I do have the 30A fuse in the box under the hood. I also have all the relays plugged in under there. I did not know that the Ford pigtail you can buy from Ford plugged in between the connections. If that is the case, I'll be picking up one of those instead. Thanks for the help.

 

The orange wire next to the blue(brake controller)wire is your positive and you will need that on your 7 wire. You dont need the back up light if your TT does not have a light on it. Mine does but cant see it anyway so its not wired.....cant see behind the TT when Iam backing up anyway...lol. Here is a good link for you

http://www.towingworld.com/info/trailerwiring.htm

 

I decided to just pony up and get the 7/4 pin harness from Ford. Replaced the factory wiring and away I go. Actually, the Wally World gizzmo I bought had wires that were too short to go the distance needed for splicing. I didn't like the idea of making more than one splice in a line.