Question about 2008 Ford F-350

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Trailer wiring 7 way

My 7 way connecter did not come with a very good diagram. The only thing it tells you is which wire is the ground. Most are color-coded, and we got the lights, brakes, and turn signals to work. We can't get the trailer brakes to work though. If I could just get a wiring diagram or something. Thanks.

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  • ttribbett Apr 21, 2009

    I have a 1997 Dodge Ram 1500 4x4 with a factory installed trailer/tow package. I have a trailer with electric brakes and in the process of wiring a 7way plug on the trailer vs. the 6way that was on it when I purchased the trailer. Double checking the wiring voltage and continuity I am unable to get a reading (voltage) on the Light Blue wire for the electric brakes. All of the other lights seem to work fine - turn signals, brake lights and running/marker lights! No actual electric brakes however! Could this be a sign of the "Trailer Relay" being bad in the Power Distribution Center (PDC) under the hood? I did find the Red 12volt wire on the Truck side of the trailer plug curroded. I have repaired that and all other wires show continuity in that section.

    I appreciate any help you can give! Thank you in advance for your HELP!

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1 Answer

DO NOT SPLICE WIRES.. You bought a 45000 dollar truck, spring for a wiring T --25 bucks.. ( plugs between main harness and Tail lights.. ) --Available at most good auto parts.. Painless wiring also has a kit.

If you did already cut or splice into your wires, take that **** loose.. Shrink wrap the dammage.. Silicone over srink wrap.. Wire will corrode.. if you did manage to get spliced wires to work,-- in a few years or sooner you will have issues with the connections..Can you say short circuit.. Moisture and loose connections are a thing of the past with sealed tap in wiring.. Plug and play..

If any of this is over your head, get a friend who knows, or a tech to help.. Don't jerry rig a 45,000 dollar new Truck.. Come ON..!!!!!

Posted on Sep 18, 2008


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2 Answers

I installed a new 7 wire connector on my wells cargo trailer, but when I connect the wires as per the color code the lights do react properly. Left signal works well, right signal flashes both tail lights...

Hi Bruce,

Let's back up for a second. Are you wired like this?

Using an inexpensive 12 V test light / tester like the one below, connect the clip to a good ground on the vehicle. Then with someone else working


the brakes, turn signals, lights, etc. ONE AT A TIME, you should push the point end of the tester into the corresponding connection on the VEHICLE. Only one connection should have power at any given time. Once you have verified that the correct & only connection has power at the right time - you can move to the trailer end of the wiring. If you can not verify the vehicle plug is working correctly - you'll have to get it working right before continuing. These connectors can develop problems over time and may need servicing.

If the trailer still has issues, check ground by uncoupling the trailer hitch from the ball on the vehicle. Keep the 7 pin connector from the trailer plugged into the vehicle and turn on the vehicle lights / have an assistant step on the brake. Connect the clip to the frame of the trailer and push the point to a good ground location on the vehicle. If the tester lights up - you have a bad ground wire between the vehicle wiring to the jack and the trailer frame somewhere. The lighting is relying on the contact between the ball & hitch for ground and could be causing the problem.

Check all the bulbs to make sure that they are the right ones and if the offset bayonet base type - inserted properly. Inspect lamp sockets, wiring and ground leads at each lamp socket. You can also disconnect a wire from a point that is common to left and right sides of the trailer to help narrow down where to look on the trailer for the trouble. If you disconnect a wire going to the left side and everything on the right works as expected when trying all the lights, brakes, etc. then you know the problem is probably on the left side. Reconnect the left side and disconnect the right side and test again. It is a process of elimination when you can't see anything obvious. Keep disconnecting 1/2 of the side that is causing trouble until you find the problem.

You can purchase a 7 wire vehicle jack test plug like this to quickly diagnose the vehicle for less than $10. It will indicate on the LEDs the power seen from the vehicle.


Mar 24, 2015 | Cars & Trucks

1 Answer

Need a schematic that shows what eachof the colors of wires should be connected to on a 7 blade RV plug in receptacle.

7-Way RV Trailer Connector Wiring Diagramqu363_250.jpg
Click to Enlargequ363_2_250.jpg
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trailer connector wireing diagram. need to know which color wire go to which post.
asked by: Joann

Expert Reply:
When wiring a trailer connector, it is best to wire by function, as wire colors can vary. We have an excellent wiring diagram on our website, I will provide you a link so you can look at it.

If you are looking at the inside of the trailer connector where the wires mount to the terminals starting at the notch at the top and working clockwise:

1:00 is Black and 12 volt power
3:00 is Green and Right Turn and Brake
5:00 is Blue and Brake Controller
7:00 is White and Ground
9:00 is Yellow and Left Turn and Brake
11:00 is Brown and Tail and Running Lights
Center is Purple and is Optional Reverse

I recommend using a circuit tester like part # 40376 to verify your connections.

Sep 12, 2013 | 2005 Dodge Ram 2500 Truck

1 Answer

Ford f350 wiring diagram

Need your model year to look up the diagram, please.

Jun 05, 2017 | Cars & Trucks

1 Answer

When I tow with my car the left blinker doesn't work on the trailer. There is a 7 pin round plug on the car, with a flat adapter to the flat pin on the trailer. I have had the same problem with at...

Hello Carol, The 7 way is for use with a brake controller and/or a trailer that has electric brakes. The 4 way flat is a basic trailer plug connector.
Connect as follows:
Green wire- Connects to the vehicles right turn wire harness & provides brake light and right turn signal on trailer.

Yellow wire- Connects to vehicles left turn wire & powers brake light & Left turn signal on trailer

White wire- Ground

Brown Wire- Tail/ marker/ license plate lights

The Blue, Red & Purple wires on the 7 way will not be used on the adapter, those are for brakes.

I hope this information is helpful.


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Here is a link to a web site that will give you the wiring diagrams based on industry standards. Your truck has 7 wires because If I remember right the 7th is for back up lights on the trailer. I have a '94 F350 with a 7 pin connector and on ly 6 wires used as my trailer doeswn't have back-up lights.

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I have a 96 ford explorer xlt with a hidden hitch. the 7 pin rv connector is not working. i found where the wires from vehicle connect to 7 pin connector and one wire was caroded at the crimp black wire...

Yes, you need the other wires to provide the trailer with battery voltage. If the trailer has trailer brakes, you should have an RV mechanic wire up the connector so the brakes on the trailer operate from the Ford.

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I have purchased a wiring harness that plugs into the factory connections. I am able to get brake lights and turn signals. The running lights do not work, also when the running lights are on the brake...

Check this location. They have color codes and wiring diagrams. Make sure the trailer has a good ground. It MUST have the ground wire connected to the truck and trailer or you will have a floating ground through the ball. That will cause blown fuses.

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2 Answers

Wiring 7 pin trailer plug for 1998 C1500 pickup truck Z71

Here is some information that I find useful when wiring trailer connectors, and the brake controller should be wired into the vehicles wiring according to the instructions that came with the brake controller and that identifies each wire from the brake controller.

Be sure that you solder all connections well for the best operation, and you should use 10 or 12 ga. wire for the Pos. (+) connection, and the ground or Neg. (-) connection, and you should run both wires all the way out to the battery, and about one foot from the battery on the Pos. (+) wire to the battery, make sure that you use a 20 or 30 amp Circuit Breaker and Do Not Use A Fuse.

The rest of these diagrams should help you to get your trailer properly wired up.







May 15, 2010 | 1999 Chevrolet Silverado 1500

2 Answers

Trailer brakes

Take a 12 volt test light... the kind that has a spring loaded clip to hold the probe into the wire, and insert it into the wire just before the trailer plug, vehicle side. (Blue I think) If there is a connection, the brake should see it and you should have an indicator light. When you activate the brake the test light should lite up. If not, move up to the brake actuator and test the blue wire. If there is nothing at the actuator, check the black wire. It is power to the controller. If no power there, check fuses again. If it does pick it up at the plug, connect the trailer and test the trailer itself. First ground to the trailer and then to the truck. Most problems are ground wire related. Then move to the axle and test it there. For the brakes to work, and even show on the indicator, there has to be a ground and power to the brakes themselves. There are 2 wires to each brake... a ground and a power. Test across both wires to make sure you have power and ground. You can also hook another trailer to your truck or another truck to your trailer. Lights can work through trailer ball ground. Brakes can't. leave the trailer unhooked from the trailer and hook the wiring up and test the lights. That usually will indicate a good or faulty ground. Also make sure there is a GOOD ground to the truck frame/body. Also try They have a great website with lots of info. Hope this helps. Mike

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Hi there;

Here is the wiring diagram for the trailer wiring for your truck.
Hope this helps

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