Wiring for trailer lights - 2002 Ford F250 Super Duty SuperCab

you must make sure you have trailer wiring converter if not factory installed. check links below for good info. press the helpful button


Troubleshooting 4 and 5 Way Wiring Installations

Fix Trailer Lights Instructions Diagrams

Testing Trailer Lights and Diagnosing Problems

Wiring Your Trailer Hitch

Trailer wiring uses the fuses for the car lights. Turn signal, running ans brake lights. Some plugs also charge the trailer battery if so wired. Check the ground wire for a good body connection. This wire often gets overlooked and can stop all trailer lights if it fails.

You have to many bulbs running for the size wire you can get into a 7 pin plug. You will have to up grade to a heavy vehicle plug which is around 2" in dia.. Next the stop light draw 25 watts each so if you have 3 trailers that ia 6 x25 watts x12 volts will indicate how many amps you are pulling when the brakes come on. Next you can change the wiring so that each bulb is connected in parallel not series that is the first 2 lights have one wire the 2nd bulbs will have a different wire out of the same pin and so on for the rest of the trailers. So what you will have will be say for 3 trailers the trailer plug will have wire to the first trailer and out of the same pin will be another wire that will go to the socket for the second trailer and so on That way the wire carrying the load will be the vehicle wire that you should have relayed any way. So you have a big current wire to the relay that is connected to the power pin of the socket. The relay is activated by the stop light wire to earth. This closes the relay and the heavy wire conducts current directly to the stop light pin of the first trailer and is piggy backed to the second socket and so on.. IN the end you will have only 2 bulbs working on each wire and not a multiple of bulbs drawing current on the one wire

Some people wire trailer plugs differently. If the plug is not wired differently than yours, make sure the tow ball is clean. No rust. That's where the trailer gets its ground from. Usually they will work if thats the case, but not right. I can't remember what the wire colors are right now. Go to etrailer and look up the diagram.

check the wires in the trailer plug as it appears that one wire is loose/broken or there is a ground wire problem
there wiring of the plug for the trailers has to be as per standards to be compatible with the box on the jeep

There are separate fuses in the fuse box for the trailer lights than for the vehicle lights. Ensure these fuses are good. The trailer lights work without any special settings on the vehicle light switch.
If you're getting no lights whatsoever (no brake, turn, or running) then you likely have a grounding issue. This is usually the white wire on the trailer lights.

Do you have a 7-wire, 6-wire, 5-wire, or 4-wire trailer light connector on the rear of your vehicle?

Your trailer connector is wired wrong or shorted. Check the connections at the car.

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Trailer Wiring Diagrams 4 Way Systems

4 way flat molded connectors allow basic hookup for three lighting functions; right turn signal / stop light (green), left turn signal / stop light (yellow), taillight / license / side marker (brown) and a ground (white).

4 way tow vehicle side.
4 way trailer side.
5 Way Systems

Same as 4 way system listed above but adds a extra blue wire for brake signal or auxiliary power. Used on pop up camper trailers or utility / boat trailers.
5 way tow vehicle side.
5 way trailer side.
6 Way System, Rectangle Plug 3/4 inch by 1 inch 6 way rectangle connectors right turn signal (green), left turn signal (yellow), taillight (brown), ground (white). The red and blue wire can be used for brake control or auxiliary. Use on a small motorcycle trailer, snowmobile trailer or utility trailer. Can also be used as custom wiring on trailers with 3 light/wire systems. See "Tow Vehicle Taillight Wiring" below.
6 way tow vehicle side.
6 way trailer side.
6 Way Systems, Round Plug

Round 1 1/4" diameter metal connector allows 1 or 2 additional wiring and lighting functions such as back up lights, auxiliary 12v power or electric brakes. Note: The black (sometimes red) 12v and blue electric brakes wire may need to be reversed to suit the trailer. Check with a test light or VOM. Uses: horse trailer, travel trailers, landscaping trailer, car trailer, etc.

6 way tow vehicle side.
6 way trailer side.
7 Way Systems

Round 2" diameter connector allows additional pin for auxiliary 12 volt power or backup lights. Uses: heavy duty landscaping trailer, car trailer, boat trailers, horse trailer, travel trailer, construction trailer, etc. Check with a test light or VOM.

7 way RV flat blade tow vehicle side.
7 way RV flat blade trailer side.

When this happens it is usually a bad earth on the trailer.But hey,check the car also.Check inside the trailer lights for a bad connection.It is an earthing problem.Mate.I hope this helps.

Well you have what is called a BUGGER.5 dont go into 4 so the problem is either the trailer is OLD and never had stop lights OR the white wire is your stop lights and it earths through the towball (but it shouldent ) so either someone has cut out the stop light wire .so check rear lights What colour is stoplight wire. As all DC wiring for trailers are 5or 7 core wires 5 for trailers and 7 for caravans..
Let me know how you get on Ron