My trailer that has electric brakes installed and a 7 prong plug connector. My Tundra has a tow package with a 7 prong plug.

Congrats, you have found Ford's super secret fuse that drove everyone mad for years!

trailers are add on package , 1st just inspect the fuses with a flashlight . as you should once a year.
http://www.tundrasolutions.com/forums/tundra/193937-blowing-tow-light-fuse/
lots of good answers here

I don\'t think it has wiring provided in the factory for the tow package either. Looking at the schematics, they appear to be different with no provision for connections. The aftermarket have a wide variety of tow packages available which are simple enough to install if you ability.

Threr is one which you have to drill a large hole in the rear bumper to fit the receiving end of the connector. This is designed so that a wide selection of adaptors can be plugged into it. The adaptors are designed to fit the fixture in the bumper and the other end is shaped to plug into what ever connector you are towing. You will find this knid of fixture on nearly any factory package.. (NO WIRES DANGLING UNDER THE VEHICLE.) additionally, when not in use, there is a spring loaded cover which closes over the fixture to keep contaminants from entering Although I am a Nissan Master techniton, I chose a long wheel base 1 ton long wheel base cab and chassis Toyota with a 3.0 V-6 which I opened the back of the cab and installed a sleeper. Then built a flatbed with removable sides. I use this to pull my Nissan 300Z race Car. I have one of these fixtures on my truck because I don\'t always use the same trailer and the connectors to the trailer for the lights and electric brakes are different. The kits come with a controler for the electric brakes which you can mount where ever you wish and the controller has adjustments to control sensitivity of the trailer brakes so you can adjust the trailer to stop with the truck about the same time instead of wearing out your brakes from the extra load. With my Toyota loades with an extra engine, transmission and diff. Air compressor. Generator. Tool box, pop up tent, oils and other fluids and other misc Items. Between the trailer, the truck and it\'s load it grosses out at 11,800 lbs.When we go to Texas world speed way, we take 45 south where where there are very few cops. We cruise at 80-85 mph in the truck without a problem If the trailer brakes don\'t work, it would take me a significant time to stop because my truck is rated for 9,500 lbs.I run the living piss out of it and it has given me no problems at all/Hmm How did I get on the subject of my Toyota flatbed? OH, it\'s because I use the trailer brake setup I described which has been flawless. There are places that specialize in selling truck accesories only. From camper top and wheels to a variety of tow packages.Check them out. Good luck..

With 4 prong and 3 extra, that will give you what you need for 7 prong for towing RV. If your not too experienced in that area, a mechanic at any trailer place, or hitch installation place or who knows RV wiring, should be able to do it for you in about 1/2 hr. or less. Testing the wires from your truck for what they do as in right , left, stop, running/taillights, etc is about the hardest part, and the 7 prong usually comes with what terminal does what.

Well the BEST way to fix that is take the Van AND Trailer to the dealer and make them check it over and get it working. Sounds like they screwed up., and are trying to blame the trailer. The 4 pins are easy to check Running lights, Left turn, Right turn and Ground. I suspect the 7 pin is wired wrong. I dont know why they put a 7 pin wiring plug on? Those are used for largeer trailers that need a battery feed and electric brakes

You have got 7 pin trailer connector that was included in the optional trailer tow package. This trailer tow package also includes an electric trailer brake wiring provision that terminates at a connector located on top of the large body harness connection under the instrument panel to the left of the break pedal, as well as an electric trailer brake pigtail harness and an instruction card that are stored in the glove box when the vehicle is shipped from the factory. You will need to add an electric brake controller of your choice that will plug-in to the harness and that will also give you power on your auxiliary circuit.

You'll have to follow the BROWN wire from the factory connector(with the running lights on of course) to the trailer connector and make sure you are getting power all the way to the two lamp fixtures. If so you've probably got two burned out 1157 bulbs or an inline fuse in the factory harness/ trailer harness.Good Luck, Dana

follow the wires back behind the bumper toward the front of the truck, check the next connector you find for corrosion.

Here's one
CAV CIRCUIT FUNCTION 1 Z13 12BK GROUND 2 B40 12LB TRAILER ELECTRIC BRAKE OUTPUT 3 L76 12BK/OR TAIL LIGHT (Trailer Tow Relay in PDC) 4 A6 12RD/TN* FUSED B(+) (40A, Always Hot, F8 in PDC) 5 L63 16DG/RD LEFT REAR TURN SIGNAL TRAILER TOW 6 L62 16BR/PK RIGHT REAR TURN SIGNAL CONNECTOR 7 L1 16VT/BK BACK-UP LAMP FIGURE 1: 7-Terminal Trailer Tow Connector

I believe you can look up the manufacturer of the trailer plug kit and find the wiring diagram there. On alot of the trailer plug kits, they have pics and diagrams in the package. The 7 pin plug (truck side) is available with the pig tail set up that plugs directly into the wiring harness for the lights. Then all you would have to worry about is the 2 wires for the electric brakes.