Trailer Wiring

Tiny
DJ2
  • 2002 CHEVROLET SILVERADO

I have a friend with a chevy truck and his trailer light plug has quit working. It was working then when they went on a trip last week it start to have intermittent problems now does not work at all. When I checked it out there was no power to any of the 3 fuses for the trailer plug. None of the schematics I've found have offered anything new. Wiring schematics and will help eliminate checking areas that are effected from whats causing the problem but I guess I wasn't quite clear, none of the fuses for the trailer plug in the fuse block have any power to them. This is the fuse block under the hood, there is no power to the fuses.

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Tuesday, August 3rd, 2010 AT 8:50 PM

66 Replies

Tiny
2CARPROS KEN
  • ADMIN
  • 7,748 POSTS

Hello,

I have found the wiring diagrams (BELOW) for the trailer. Here is a guide to help you troubleshoot the problem.

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

If the fuse does not have power to it then it has to be a wiring issue because power comes from the battery to the fuse box. If surrounding fuses have power than the box itself is probably not at fault, although this does not eliminate that possibility completely. You will need to inspect the wiring going to the box and right under the box where they all connect. If the wiring is good then a swap of the fuse box with known good one will need to be made.

Please let us know if you need anything else to get the problem fixed.

Cheers, Ken

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Monday, May 22nd, 2017 AT 11:54 AM
Tiny
BASS202
  • 2004 CHEVROLET SILVERADO

Electrical problem
2004 Chevy Silverado V8 Two Wheel Drive Automatic 103000 miles

I am having problem with trailer lights. I have tried on 3 different trailers. So it isn't in the trailer. When I turn the left turn signal it works correctly. When I turn the right turn signal on both the right & left turn light blink. I have no left brake light.

I test the wires with a test light on the trailer plug (factory wired 7-pin) & it test the same way as above, so I am sure it is not a ground problem.

The lights on the back of pickup works correctly.

Thanks,
Randy

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Monday, May 22nd, 2017 AT 12:29 PM (Merged)
Tiny
RHALL77
  • MEMBER

Check the wires going to the trailer and make sure none have rubbed through. Sounds like they are shorting out together. When they all blink are they dim. If they are, sounds like they would be shorting to that ground.

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Monday, May 22nd, 2017 AT 12:29 PM (Merged)
Tiny
BASS202
  • MEMBER

I check the wiring on the pickup & found nothing rubbed. If there were two wires shorting across I think that both the turn signal would flash when the right or left turn signal was turned on. Like I said when I turn the left signal on only the left signal blinks.

Thanks,
Randy

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Monday, May 22nd, 2017 AT 12:29 PM (Merged)
Tiny
RHALL77
  • MEMBER

Thats not true wiring can do some wierd things. Now when they are both blinking aare they both very bright, or is the one that is not suppose to be blinking dim.

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Monday, May 22nd, 2017 AT 12:29 PM (Merged)
Tiny
BASS202
  • MEMBER

The only time they both blink is when the right signal is turn on. The left one works correctly, but the left brake light does not work. Yes both lights are bright.

Thanks,
Randy

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Monday, May 22nd, 2017 AT 12:29 PM (Merged)
Tiny
RHALL77
  • MEMBER

Here is the wiring diagram for the trailer lights


http://www.2carpros.com/forum/automotive_pictures/166241_1248577_1.jpg

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Monday, May 22nd, 2017 AT 12:29 PM (Merged)
Tiny
DALECLEM
  • MEMBER

I had the same problem on my 04 silverado. It ended up being the factory trailer plug. I bought a new one from the dealer and it fixed the problem. I first looked for corrosion but didn't find any.

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Monday, May 22nd, 2017 AT 12:29 PM (Merged)
Tiny
FDFAIRLN
  • MEMBER

Did you ever solve this problem? I have a very similar problem.

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Monday, May 22nd, 2017 AT 12:29 PM (Merged)
Tiny
DALECLEM
  • MEMBER

Yes, bought the female plug for the truck from the chevy dealer. When you have speperate stop and signal lights you need a converter to get it to work on a trailer with integral lights. There must be some diodes in the plug that we can't see. Good luck.

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Monday, May 22nd, 2017 AT 12:29 PM (Merged)
Tiny
FDFAIRLN
  • MEMBER

Actually, after much surfing today, I got an idea. I knew the trailer I was trying to hook up to had some poor wiring. When I hooked up the trailer to the truck, I blew all the fuses for the trailer side of the turn signals. Unfortunately, the fuses did not protect the flasher relay. The relay has contacts for the trailer and truck separately. I discovered the relay going to the trailer had fused. Managed to take the relay apart and pry the fused relay apart. Works fine now. Beats paying $97 at the dealer for a new one!

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Monday, May 22nd, 2017 AT 12:29 PM (Merged)
Tiny
DEBENDERLE
  • 2004 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 120,000 MILES

When the trailer is plugged into my son's truck everything works perfect, when plugged into the chevy and the left turn signal is on both the sides blink

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Monday, May 22nd, 2017 AT 12:29 PM (Merged)
Tiny
CJ MEDEVAC II
  • MEMBER

SOUNDS LIKE A PROBLEM WITH THE CHEVY

USE A 12 VOLT TEST LIGHT--GROUND IT REAL WELL NEAR THE PIG TAIL

HERE'S WHAT YOU SHOULD GET

BROWN WIRE PIN---STEADY TEST LIGHT

GREEN WIRE PIN--RIGHT TURN --BLINKING TEST LIGHT (IF YOU TURN OFF THE TURN SIGNAL, APPLY BRAKES AND GET A STEADY TEST LIGHT)

YELLOW WIRE PIN--LEFT TURN--BLINKING TEST LIGHT (IF YOU TURN OFF THE TURN SIGNAL, APPLY BRAKES AND GET A STEADY TEST LIGHT)

WHITE WIRE--IS THE GROUND--IT NEEDS TO BE GROUNDED ON THE VEHICLE AND NOT DEPEND ON THE TOW BALL AS A GROUND FOR THE TRAILER

THINGS TO REMEMBER---THE TRAILER HAS 2 FILAMENTS IN THE BULBS, ONE WILL "BURN" (RUNNING LIGHTS) THE OTHER WILL BE REALLY BRIGHT (THIS WOULD BE THE TURN SIGNALS/ BRAKE LIGHT FILAMENT)

SO MANY PEOPLE WILL HOOK UP THEIR LIGHTS SO THAT THE RUNNING LIGHTS AND TURN/ BRAKES ARE REVERSED

THE TURN AND BRAKES ARE NOW DIM, AND THE RUNNING LIGHTS ARE BRIGHT - EVEN ONE SIDE OF THE TRAILER IS CORRECT AND THE OTHER SIDE IS WRONG

MUCH OF THE TIME YOU HAVE A GROUNDING PROBLEM, THIS MAKES CORRECTLY HOOKED UP LIGHTS "SEEK GROUND" WHEREVER IT CAN (THRU THE OTHER WIRE) LIGHTS MAY BLINK DIM, EVEN BOTH FILAMENTS WILL BLINK)

I HAVE MADE SEVERAL REALLY LONG ALLIGATOR CLIP JUMPER WIRES

WHEN I TEST, I GROUND TO THE BATTERY NEGATIVE POST (A GROUND DON'T GET NO BETTER'N THAT!

I REMOVE THE LENSES AND CONNECT (OR TOUCH) MY JUMPER TO THE PLATE INSIDE THE LIGHT FIXTURE. IF THIS WORKS WELL, EITHER MY LIGHT'S GROUND IS RUSTY, OR THE GROUND FROM THE TOW VEHICLE IS BAD

REMOVE THE BULBS, LOOK INTO THE BOTTOM OF THE SOCKETS, IS THE CONNECTION THERE? IS IT MELTED? HAS ONE OF THE PINS SUCKED BACK UP INSIDE THE SPRING LOADED BOTTOM?

HAS SOMEONE INSTALLED INCORRECT BULBS? LAST ONE I DEALT WITH, SOMEONE INSTALLED, RATHER "CRAMMED" "1156" (SINGLE FILAMENT) BULBS IN INSTEAD OF "1157" DUAL FILAMENT BULBS

SENDING A PIC OF MY TEST LIGHT IN ACTION (ANOTHER KINDA USE FOR IT) A VOLT METER WILL WORK IF YOU HAVE ONE

KEEP US POSTED ON PROGRESS

THE MEDIC

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Monday, May 22nd, 2017 AT 12:29 PM (Merged)
Tiny
VIC GAIGALS
  • 2001 CHEVROLET SILVERADO

Electrical problem
2001 Chevy Silverado V8 Four Wheel Drive Automatic 64233 miles

the trailer connector on the truck came from the factory. I tested the continuity on plug ok. The brown wire that says on outside cover says running light the shop manual ligthing system 8-321 shows it going to a trailer park inline fuse. All the fuses in the fuse box are ok. The brown wire has always been dead. Is there a inline fuse and where or how can I fix it without giving GM a blank check to fix it

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Monday, May 22nd, 2017 AT 12:29 PM (Merged)
Tiny
MERLIN2021
  • EXPERT
  • 17,547 POSTS

That brown wire is only "hot" with the park lamp relay enegized. Top picture is light duty hitch, bottom is heavy duty.


http://www.2carpros.com/forum/automotive_pictures/62217_trailera_1.jpg



http://www.2carpros.com/forum/automotive_pictures/62217_trailerb_1.jpg

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Monday, May 22nd, 2017 AT 12:29 PM (Merged)
Tiny
VIC GAIGALS
  • MEMBER

Thank you well done. It looked like there was a in line fuse looking under truck. Thank you again

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Monday, May 22nd, 2017 AT 12:29 PM (Merged)
Tiny
MERLIN2021
  • EXPERT
  • 17,547 POSTS

Your welcome!

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Monday, May 22nd, 2017 AT 12:29 PM (Merged)
Tiny
DENNIS OGRADY
  • 2003 CHEVROLET SILVERADO

Electrical problem
2003 Chevy Silverado V8 Four Wheel Drive Automatic 140000 miles

the truck has a factory installed tow package the wireing is in very good condition.
When the left turn signal is turned on the trailer four way flashers go on for the trailer when the brakes are used only the left brake light on the trailer works all other lights work as they should right turn signal flashers and running lights work correctly I have checked on other trailers and the problem is the same so it is not the trailer lights I have tried different plug in units with same results

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Monday, May 22nd, 2017 AT 12:29 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
  • 68,290 POSTS

Identify the left and right signal power supply on the truck. Turn the left signal on and let me know if you are getting power from both the left and right power supply wires.

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Monday, May 22nd, 2017 AT 12:29 PM (Merged)
Tiny
DAVIDSLUSHERMCGMAILCOM
  • 2004 CHEVROLET SILVERADO
  • 6.6L
  • V8
  • TURBO
  • 4WD
  • AUTOMATIC
  • 160,000 MILES

I had a brake connector wired into the bed for a 5th wheel. When I bought the truck the factory 7-pin on the bumper was corroded so I bought a new one. When the shop wired the connectors now when I press on the brakes my left marker lights come on but the brake controller isn't sending power to my trailer brakes. I'm not sure which wire is ran wrong?

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Monday, May 22nd, 2017 AT 12:30 PM (Merged)

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