(Another) Trailer Wiring Question

82renken

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Nov 25, 2010
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I am trying to wire a standard (white, green brown yellow) flat four wire connector to a 1982 vintage trailer that had a socket type connector that the previous owner cut off from the trailer wires. The problem that I am running in to is that the wires on the trailer are green, brown, yellow, and blue. When I match up the corresponding colors with the white on the new plug connected to the blue on the trailer both turn signals blink when I activate either direction on the tow vehicle. I've tried a couple of different color combos and either both turn signals flash on neither will work. The brake lights work when I connect the white to blue. Other than rewiring the trailer am I missing something? Thanks.
 

dockwrecker

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Re: (Another) Trailer Wiring Question

The white is Ground
The brown is running
Yellow is left turn
Green is right turn
The blue one on your trailer is God Knows What, but is usually blue for electric brakes. (which I bet you don't have.)
 

lncoop

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Re: (Another) Trailer Wiring Question

Might try temporarily grounding the white wire to the trailer frame while leaving the Y/G/B wires matched. I've found that usually gives me enough ground to test for proper functionality. Once you get everything squared away you can ground properly.
 

Bob's Garage

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Re: (Another) Trailer Wiring Question

The white is Ground
The brown is running
Yellow is left turn
Green is right turn
The blue one on your trailer is God Knows What, but is usually blue for electric brakes. (which I bet you don't have.)

The blue wire on a boat trailer is the connection for the backup lights on the tow vehicle to the anti-reverse solenoid used on trailers with disc brakes.

This is found when using a flat 5 pin connector.

The electric brakes would be found on a 7 pin connector, as on an RV and the electric brakes work off their own circuit. This is because the blue wire only has current flowing when the tow vehicle's brakes are applied. Electric brakes require a constant current flow so the brakes can be applied even if the vehicle's brakes are not.

Using the trailer brakes in this fashion lets the trailer slow the vehicle, and takes some of the strain off going down mountains. Same information holds true for the electric/hydraulic set ups.

So - if your trailer has a blue wire it may have disc drakes and if so you need to use a 5 pin connector. Either that or get out and block the coupler from sliding back each time you want to reverse your direction.
 

dockwrecker

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Re: (Another) Trailer Wiring Question

The blue wire on a boat trailer is the connection for the backup lights on the tow vehicle to the anti-reverse solenoid used on trailers with disc brakes.

This is found when using a flat 5 pin connector.

The electric brakes would be found on a 7 pin connector, as on an RV and the electric brakes work off their own circuit. This is because the blue wire only has current flowing when the tow vehicle's brakes are applied. Electric brakes require a constant current flow so the brakes can be applied even if the vehicle's brakes are not.

Using the trailer brakes in this fashion lets the trailer slow the vehicle, and takes some of the strain off going down mountains. Same information holds true for the electric/hydraulic set ups.

So - if your trailer has a blue wire it may have disc drakes and if so you need to use a 5 pin connector. Either that or get out and block the coupler from sliding back each time you want to reverse your direction.

Not quite. The blue terminal is for electric trailer brakes on a typical 5 wire. A 7 pin connection for a reverse solenoid is from the center pin of the connector for the reverse lights, coded green. Tie Down reverse solenoids use a blue wire from the solenoid (another statement of the quality of Tie Down) but it technically should be green. The original poster needs to clarify his brake system to make the correct call. The blue wire on a 7 pin is connected to a brake controller for electric brakes if so equipped, and not common to most boat trailers.
 

82renken

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Re: (Another) Trailer Wiring Question

I'm sorry...I should have stated in the original post. The trailer does not have any brakes (not even surge).
 

Bob's Garage

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Re: (Another) Trailer Wiring Question

Not quite. The blue terminal is for electric trailer brakes on a typical 5 wire. A 7 pin connection for a reverse solenoid is from the center pin of the connector for the reverse lights, coded green. Tie Down reverse solenoids use a blue wire from the solenoid (another statement of the quality of Tie Down) but it technically should be green. The original poster needs to clarify his brake system to make the correct call. The blue wire on a 7 pin is connected to a brake controller for electric brakes if so equipped, and not common to most boat trailers.

Well, after looking at all the various instructions for wiring trailers I have come to the conclusion that there are numerous ways to connect the wires by color, but only one correct way by function.

It seems that there are some sites that agreed with me that the 5th, blue, wire is attached to the backup lights on the vehicle, while others indicate it is for the electric brakes. Some indicate the 5th wire on the flat plug is red although I have never seen it that way. (I suspect this is more a matter of semantics as in either case the wire is "hot" only when the brake pedal is depressed.)

Also, some 7 wire connectors reverse the center pin and "S" pins function.

Apparently there is no absolutes when it comes to the wiring, even vehicle manufacturers use different colors for the functions, even changing them over the years.

The best advise, I have concluded, is to verify the function of the individual wires at the tow vehicle's connector with a meter or test light, then make the appropriate connection based on your findings. Use the trailer plug wiring color code to attach to the correct color wire coming off the tailer lights, which I think use the same code universally.

I would suggest (this is what I would do in your situation), that you remove all of the old wiring up to the lights and begin fresh. You will find it much easier than trying to second guess the previous owner, and you will have fresh wires for your system.
 

jayhanig

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Re: (Another) Trailer Wiring Question

The best advise, I have concluded, is to verify the function of the individual wires at the tow vehicle's connector with a meter or test light, then make the appropriate connection based on your findings. Use the trailer plug wiring color code to attach to the correct color wire coming off the trailer lights, which I think use the same code universally.

I would suggest (this is what I would do in your situation), that you remove all of the old wiring up to the lights and begin fresh. You will find it much easier than trying to second guess the previous owner, and you will have fresh wires for your system.


If you're going to go to that much trouble, the least you can do is to continue on with the standardized trailer color codes when rewiring your truck's connector. It will make troubleshooting much easier in the future:

Green = Right Turn and Stop
Yellow = Left Turn and Stop
Brown = Running and Parking Lights
White = Ground to vehicle.
Blue (optional) = Solenoid or Electric Brakes

If you use a round connector rather than a flat, Black should be from your truck's 12V hot to the center post on the jack. The colors on the outside of the jack should be the same as on the flat connectors. Any additional pins can be used for accessories.
 

dockwrecker

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Re: (Another) Trailer Wiring Question

I need to correct an earlier post of mine, the reverse light center pin on a 7-wire is not green. (you'll see I've already hooked that one up to the right turn in a previous post... duh on me.) And Bob has apparently found the Cal Trans version of the 7 pin showing the center pin as blue for brakes. The correct color after further review should be ORANGE :)eek:) for a reverse solenoid designating it as an auxiliary circuit connected to the backup lights.
How ya like the mud now????
 
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