Trailer Wiring Issue

[VortecZ71]

So I just bought a brand new dual axle utility trailer. My cousin had to tow it home from the dealer because something is wrong with the wiring on my truck. Everything worked fine when my cousin towed it with his 05 Silverado so I doubt something is wrong with the trailer itself. I have an 03 Silverado with the factory tow package. The brake lights and turn signals work fine on the trailer during the day with my lights off. However, when I have my headlights on and I use either blinker, everything on the trailer just flashes including all the clearance lights. Also, when I press my brakes, the taillamps go out. Anybody have any idea as to what might be causing this? I'll try to get a video up when I can.

 

[KB9UDE]

Sounds like a bad Ground connection to me.

 

[brokenknee]

Sounds like a bad Ground connection to me.

I agree, that would be the first thing I would check.

 

[outinthetalgrass]

I second that... bad ground between truck and trailer.. when lights are off tail light and turn signals using light circuit for ground.

 

[Dmace]

I agree with a bad ground being the problem. Try taking a jumper wire (wire with two alligator clips on it) and connecting it to bare metal on the trailer and bare metal on the truck and see if it helps.

 

[jeffsw6]

I think your truck's connector is wired differently and what should be the ground is really connected to the trailer relay for your headlights, which is probably grounded except when you turn the lights on?

I think this is the most common wiring scheme: http://www.cumminsforum.com/forum/a...-pin-connector-wire-colors-7waytrailerend.jpg Keep in mind this will look right/left swapped depending on which way you are looking at the connector, e.g. the trailer's socket or the vehicle's plug.

I would get a friend and a VOM or 12V lamp and loose wire, and test what is really coming from the connector on your truck. If it's not right just change it. If you don't have a soldering iron and heat shrink kit (or are like me and can't hold your hand steady enough to solder) then get someone to correct it for you.

It is possible it could be a more complicated problem but I seriously doubt it. I have seen other 7-wire schemes and the auto parts store I go to even has some adapters on the shelf to go from one kind of 7-wire to a different kind.

 

[grsthegreat]

i have never seen a factory wired tow package that isnt wired correctly, cause there usually plug and play systems. I DO know that a bad ground will play havoc with trailer wiring. Ive had it myself many times. I agree on testing it with a separate wire connecting a good ground sorce to the trailer and see what happens.

On the wifes 94 dodge ram truck, i found the ground wire had rotted away where it bolted onto the frame

 

[Mike_VT]

Agree, sounds like a bad ground. Jump it and test with separate ground wires.

 

[deepNdirt]

Here is a wiring diagram, and a cheap tester I use to help troubleshoot trailer lighting problems,

 

[MF 1532]

I sell trailers , the above posts are all good places to start , ground . I have people hook up to a trailer and I hear ''somethings wrong with the trailer wiring '' . For 6 or 7 $ I have 3 different test plugs I can plug into their truck , and I don't recall it ever being the trailer . The first time I had someone state their dome light in the trailer didn't work was the head scratcher . Now I know to look at truck auxillary trailer fuse . Some manufacturers put a dummy fuse in . Anyway if you ' ll pickup one of those testers life will be simpler .:thumbsup:

 

[Soundguy]

i'd also check ground first. use a set of jumper cables as the test.. clip to truck and trailer frame

 

[Diamondpilot]

If the trailer has brakes many of the early 2000's GM were wired wrong, or differently. I also sell trailers and have ran into this a few times. I have also seen many of the GM 7 pin round plugs internally corroded causing issues.

Chris

 

[brokenknee]

Here is a link to etrailer on how to trouble shoot wiring problems.

Trailer Wiring Diagrams | etrailer.com

Let us know what you found.

 

[turbo660]

If the trailer has brakes many of the early 2000's GM were wired wrong, or differently. I also sell trailers and have ran into this a few times. I have also seen many of the GM 7 pin round plugs internally corroded causing issues.
Chris

I had a similar problem with my 1999 silverado 1500, all I needed to do was unplug the wiring harness at the back of the 7 pin connecter, clean the corroded contacts and plug back in . Worked fine ever since.
Easy to check no cost solution.

 

[Soundguy]

on my 2000 yukon, I had to swap a wire inthe trailer plug adapter. that fixed it for me.