Question about GMC C3500

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Trailer wiring Year 2007. Right and left blinkers work on truck however when I plug in the trailer they do not work.

Posted by Anonymous on


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Posted on Jan 02, 2017

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I'd get a 12vdc test light if you don't have one already & start from plug, and keep probing back from there. It may be as simple as a bad connection under truck where joined into harness.

Posted on Nov 29, 2008

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SOURCE: Hooked my 2007 Sprinter camping trailer to the

Is this a 4 way or 6 way connection system? If your truck is wrong, then all factory equipped trailer package harnesses would be wrong, tell your trailer guy...I don't think so.
Is this the first trailer you have hauled?
Let me know, and we will go from there.

Posted on Mar 10, 2009

  • 1779 Answers

SOURCE: I have a problem with the trailer light connector

Check the plug at the back of the truck for corrosion. The brown wire entering the truck plug should be the the running lights, if no juice at truck plug in, you need to trace it back to the source looking for broken, pinched, wires, or poor connections.

Posted on Apr 16, 2009

  • 676 Answers

SOURCE: 2005 silverado trailer wiring

You may want to get a ground loop isolator or even cheaper. Go to radio shack and buy two 1amp diodes and put them on each turn signal wire. This will eliminate the problem. The diode will be black with a gray line. the line will go towards the trailer on each wire. this should take care of the problem.

Posted on May 08, 2009

  • 174 Answers


I have seen once before that the fuse box was bad on a 2003 Dodge 3500. I had power in and nothing out. We had to replace the box. Not cheap! Hope it is simple like a loose connection though. I think I had to pull the inner fender on the drivers side to access the bottom of the fuse box. Pain in the ****, but...

Posted on Oct 01, 2009

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1 Answer

I do not have left turn signal at the trailer plugs but have on the truck itself, is there a something I can do to get the left blinker on the trailer

check for lh blinker power in the both plug connections to ensure that the power is getting to the plugs from the vehicle harness
then check the wiring from the plug to the lh blinker lights

Nov 21, 2016 | Cars & Trucks

1 Answer

How do I rectify indicator lights not working at all, on a 2003 Toyota Prado (Petrol)

If the blinkers on the car are working when the trailer is not connected but they fail when you connect the trailer plug, it is because the LOAD of the bulbs on the trailer exceed the capacity of the BLINKER CIRCUIT of the vehicle. I would recommend replacing the tail lights on the trailer with LED tail lights. Did that on my travel trailer, and it solved the problem 100%

May 09, 2015 | Toyota Cars & Trucks

1 Answer

I want to get my trailer lights working. I have running lights, but no left or right blinker. I have power going into the t connector, and running lights coming out, but no left or right coming out. w

use a multi meter to find which pin has the power when the light is operating and match the trailer wire to that pin. There is a standard code for wiring trailer plugs but some people ignore it and then when different trailers are connected some items do not work.

Nov 12, 2014 | Cars & Trucks

1 Answer

Where can i find a identification diagram for a fuse box on a 2007 dodge ram 1500?

Unless I'm mistaken, there is no fuse dedicated to the trailer lights - they're wired directly to the matching truck lights - the running lights & taillights should be wired directly to your truck's taillights.

Check your trailer wiring from the truck plug all the way back. I've seen lots of poor connections in the truck plug, as well as any of those squeeze splices you might have in your trailer. Look also at the ground wiring for your running lights.

Aug 01, 2014 | 2007 Dodge Ram Truck

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.


Sep 18, 2011 | Honda Accord Cars & Trucks

1 Answer

When i turn the left blinker on both left and right blink on just the trailer plug. right blinker works fine.

you seem to have problem with the wiring of the trailer plug, you need to check that the correct color wire is in the right position in the plug, or the problem may be in the outlet plug of the vehicle, you will need to check both plugs & make sure that they are wired correctly......hope this helps......cheers.

Aug 01, 2011 | 2003 Chevrolet Silverado 2500HD

1 Answer

Trailer wires what is what??

On trailer plug, white is ground,yellow is left turn signal,green is right turn signal & brown is tailights.

Jun 08, 2010 | 2001 Ford Focus

2 Answers

Utility trailer wiring to 1998 Dodge Carivan

Trailer end; Red=Brake
Brown=Running lights
You will need a turn and brake signal box IF, you have different bulbs for brake and turn lamps. If the brake and turn bulbs are one(red)lens than no box will be required. Thanks, Dana

Sep 28, 2009 | 1998 Dodge Grand Caravan

1 Answer

2005 silverado trailer wiring

You may want to get a ground loop isolator or even cheaper. Go to radio shack and buy two 1amp diodes and put them on each turn signal wire. This will eliminate the problem. The diode will be black with a gray line. the line will go towards the trailer on each wire. this should take care of the problem.

Mar 28, 2009 | 2005 Chevrolet Silverado

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