trailer wiring harness question
Thread Starter
Joined: Oct 2008
Posts: 2
trailer wiring harness question
Hello all, I'm brand new and don't know my way around very well, so forgive me if this question is slightly misplaced. I'm trying to put a vehicle wiring harness (4-way) onto my 2001 Blazer. When I dug around underneath the back, I uncovered some bundled up wiring that looked like its what I would attach the wiring to (i call this a 'pigtail', is that good vernaculer?) At any rate, the wire colors are yellow, green, brown, blue. Can anyone tell me what these are for? Left/Right blinkers? Brakes? Ground? Reverse? Thanks so much for any help.
Super Member
Joined: Oct 2007
Posts: 1,244
From: Long Island
RE: trailer wiring harness question
what you found is for the trailer Wires, you can either put a 4 wire flat connector or a 4pin round connector, i put the 4pin round on mine right thru the hole where you would put the pole to lower the tire from underneath.. My spare is inside so thats why i used that spot..I`ll try and get pics for you.
Brown= Parking lights
White= Ground
Yellow= Right turn
Green= Left turn
Brown= Parking lights
White= Ground
Yellow= Right turn
Green= Left turn
Thread Starter
Joined: Oct 2008
Posts: 2
RE: trailer wiring harness question
Thanks 2002extreme. I've dug around some more and now have 6 wires and a mostly illegible tag to identify them. (I didn't peel back enough tape to notice all the wires, some were shorter) I now have white, light green, dark green, yellow, brown and blue. What little I can make out from the tag says...
wht - grd
grn dk - rh turn
yel - lh turn
brn - rr lps
grn lt - bu lps
blu lt - ???? ?toflp (complete mystery)
Some of those are self explanatory, some aren't. Does this change anything for the 4 wire? or does your color scheme still hold up? Again, many thanks.
wht - grd
grn dk - rh turn
yel - lh turn
brn - rr lps
grn lt - bu lps
blu lt - ???? ?toflp (complete mystery)
Some of those are self explanatory, some aren't. Does this change anything for the 4 wire? or does your color scheme still hold up? Again, many thanks.
BF Veteran
Joined: Jan 2008
Posts: 2,750
From: Southern, Alberta
RE: trailer wiring harness question
The color scheme is still the same. The Blue and LT Green won't be used unless your trailer has reverse lights and brakes, and you need a brake controller to use the blue one.
New Member
Joined: Jun 2009
Posts: 76
this post answered most of my questions but i have a couple more. so you wont have brake lights if you use the yellow,green, white, and brown? Also i have one of the lighted deals that slides into the receiver and the chevy bowtie lights up. the only wires on it are green and white. when i plug it in it only works when the right turn signal is working and it flashes. whats the deal here?
BF Veteran
Joined: Mar 2008
Posts: 3,286
From: Auckland, New Zealand
Ken, the blue wire is for electronic brakes, not for the brake light.
Here is a quote from another thread also dug up:
The brake lights on a trailer are a combination of the L & R turn circuits. In a typical 4-pin configuration, there is no true brake circuit. As an example, when you depress the brake pedal, the yellow and dark green wires get +12V constant. If you are pressing the brake pedal and the left turn signal, then the dark green wire would have +12V constant and the yellow wire would have intermittent +12V from the flasher module.
If the lighted hitch cap only uses wiring available in the 4 pin connector, then it is limited to the functions available.
Here is a quote from another thread also dug up:
Hmm.. Never heard of an aftermarket owners manual... You could always sign up at MyGMLink.com and download a copy of your factory owners manual...
Trailer Wiring Harness
The light-duty trailer wiring is a six-wire harness assembly. The optional heavy-duty trailer wiring is an eight-wire harness assembly. The harnesses are stored under the vehicle, along the passenger-side frame crossmember on two-door vehicles or on the driver's side corner frame rear crossmember on four-door vehicles. The heavy-duty trailer wiring is fused in the engine compartment fuse block. See Fuses and Circuit Breakers on page 5-88. Both harnesses have no connector and should be wired by a qualified electrical technician. The technician can use the following color code chart when connecting the wiring harness to your trailer.
Securely attach the harness to the trailer, then tape or strap it to your vehicle's frame rail. Be sure you leave it loose enough so the wiring doesn't bend or break, but not so loose that it drags on the ground. Store the harness in its original place. Wrap the harness together and tie it neatly so it won't be damaged.
The light-duty trailer wiring is a six-wire harness assembly. The optional heavy-duty trailer wiring is an eight-wire harness assembly. The harnesses are stored under the vehicle, along the passenger-side frame crossmember on two-door vehicles or on the driver's side corner frame rear crossmember on four-door vehicles. The heavy-duty trailer wiring is fused in the engine compartment fuse block. See Fuses and Circuit Breakers on page 5-88. Both harnesses have no connector and should be wired by a qualified electrical technician. The technician can use the following color code chart when connecting the wiring harness to your trailer.
- Dark Blue: Use for electric trailer brakes or auxiliary wiring (eight-wire harness only).
- Red: Use for battery charging; it connects to the starter solenoid (eight-wire harness only).
- Light Green: Back-up lamps.
- Brown: Taillamps and parking lamps.
- Yellow: Left stoplamp and turn signal.
- Dark Green: Right stoplamp and turn signal.
- White: Ground wire.
- Light Blue: Auxiliary stoplamp.
Securely attach the harness to the trailer, then tape or strap it to your vehicle's frame rail. Be sure you leave it loose enough so the wiring doesn't bend or break, but not so loose that it drags on the ground. Store the harness in its original place. Wrap the harness together and tie it neatly so it won't be damaged.
If the lighted hitch cap only uses wiring available in the 4 pin connector, then it is limited to the functions available.
Starting Member
Joined: Jul 2010
Posts: 1
i have a 96 blazer. it has a 4 wire trailer wire connector. everything appears to be hooked up correctly but i cannot get any power to the wires at any time. does anyone know if there is a fuse for these somewhere? the owners manual says that there is one located at the drivers compartment fuse block but i cannot locate it. please help.
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