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Factory Trailer Wiring?

GMCanuck

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GMCanuck Enthusiast

GMCanuck

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Okay, so I checked the 7-pin plug on my '06 today to see what is what, and am curious how GM has these configured, since as a Z71, it came wired from the factory (at least that is what the build sheet says).

 

Results...

 

12V power - good

Tail lights - good

Left turn - good

Ground - good

 

The questions are...

 

1) 12V power - along with powering 12V trailer items (inside lights, furnace fan, etc.) can this also be used to "trickle charge" an RV/marine battery on the trailer during towing? That's how my trailer is currently wired.

 

2) Right turn signal - should I assume a wire is cut somewhere, or am I looking for a fuse (truck signal light works fine)?

 

3) Electric brakes - when should this contact have power, 'cause pressing the brake pedal does not do it? I do not have a trailer with electric brakes, but I am still curious.

 

4) Auxiliary (center) wire - what is this usually used for. I would like to use it for back-up lights, which I installed on my trailer, but was wondering what it is usually for.

 

5) Extra Wire - in behind the hitch-mounted plug, coming from the harness, is another thin wire with an unique end on it, covered with a rubber protective "cap". Any idea what this wire is used for - assuming it's a GM factory thing?

 

 

Any thoughts - thanks.

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jrod332 Enthusiast

jrod332

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I know for the brakes to work you need a brake controller. That wire wont have power until it is connected to a controller and plugged into the truck. As far as charging. Im not sure where the power comes from. I have a trailer with electric brakes and it has small battery in a breakaway box in case it comes loose on the road, and it gets charged from the truck when its connected.

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watchdog218 New Member

watchdog218

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the trlrs i'm familiar with, (travel trailers), use the center pin (aux) for powering the trailer interior items and charging the trailers battery if your converter supports this. the 12v power wire is uesed to power your stop/turn signal lights. and yes the blue wire should not power unless you have a brake controller hooked up.

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compulynx Enthusiast

compulynx

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The center pin is for backup lights on your truck. That is the way it is wired. The 12v does NOT power the brake-tail lights...it is for the trailer 12v power. And yes, it will charge the battery on the trailer when towing if it is wired correctly. The LH-RH brake/turn and tail lights have their own wires....

 

 

There were some older trailers that would use the center pin for power, but no newer ones....

 

I will repost the diagrams...The top is the truck, the bottom one is looking at the trailer connector from the rear, not in to it....The orange aux wire is not used in newer camper trailers....On the truck, it is wired to the backup lights.

 

I will add that some of the confusion comes about because the older round 6 wire system DID use the center conductor for the trailer battery.

 

 

con2.jpg

 

EDIT: I just noticed you have a GMT800. The above is the GMT900. I am not sure if the GMT800 had the center hooked to backup lights. It may have just not had a connection on those.

C

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MS3DALE Senior Enthusiast

MS3DALE

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5) Extra Wire - in behind the hitch-mounted plug, coming from the harness, is another thin wire with an unique end on it, covered with a rubber protective "cap". Any idea what this wire is used for - assuming it's a GM factory thing?

 

This one is for a third brake light.

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GMCanuck Enthusiast

GMCanuck

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i dont understand what you dont understand

 

I did not understand the comment about the constant 12v being used to power the stop/turn signal lights. I know our Rav4 has an additional power lead to the back, but that is used to power the trailer lights, since the Rav uses low-voltage LED tail/brake lights. But the Sierra has regular filiment bulbs - why do these require constant 12v?

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GMCanuck Enthusiast

GMCanuck

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The center pin is for backup lights on your truck. That is the way it is wired. The 12v does NOT power the brake-tail lights...it is for the trailer 12v power. And yes, it will charge the battery on the trailer when towing if it is wired correctly. The LH-RH brake/turn and tail lights have their own wires....

 

 

There were some older trailers that would use the center pin for power, but no newer ones....

 

I will repost the diagrams...The top is the truck, the bottom one is looking at the trailer connector from the rear, not in to it....The orange aux wire is not used in newer camper trailers....On the truck, it is wired to the backup lights.

 

I will add that some of the confusion comes about because the older round 6 wire system DID use the center conductor for the trailer battery.

 

 

con2.jpg

 

EDIT: I just noticed you have a GMT800. The above is the GMT900. I am not sure if the GMT800 had the center hooked to backup lights. It may have just not had a connection on those.

C

 

Thanks Man - that's perfect. It was kind of dark in the garage when I was playing with this before, and I certainly did not expect the plug cover to have this wiring schematic on it. But I just went and looked again and sure enough...

 

So I guess this means that my test light should light if I have the truck in reverse and I contact the center pin (and ground of course)? If so, I guess I have a bad wire somewhere, 'cause there is nothing there. Same for the right turn/stop.

 

I guess the hunt is on... :)

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kpruitt Enthusiast

kpruitt

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The center pin is for backup lights on your truck. That is the way it is wired. The 12v does NOT power the brake-tail lights...it is for the trailer 12v power. And yes, it will charge the battery on the trailer when towing if it is wired correctly. The LH-RH brake/turn and tail lights have their own wires....

 

 

There were some older trailers that would use the center pin for power, but no newer ones....

 

I will repost the diagrams...The top is the truck, the bottom one is looking at the trailer connector from the rear, not in to it....The orange aux wire is not used in newer camper trailers....On the truck, it is wired to the backup lights.

 

I will add that some of the confusion comes about because the older round 6 wire system DID use the center conductor for the trailer battery.

 

 

con2.jpg

 

EDIT: I just noticed you have a GMT800. The above is the GMT900. I am not sure if the GMT800 had the center hooked to backup lights. It may have just not had a connection on those.

C

 

Thanks Man - that's perfect. It was kind of dark in the garage when I was playing with this before, and I certainly did not expect the plug cover to have this wiring schematic on it. But I just went and looked again and sure enough...

 

So I guess this means that my test light should light if I have the truck in reverse and I contact the center pin (and ground of course)? If so, I guess I have a bad wire somewhere, 'cause there is nothing there. Same for the right turn/stop.

 

I guess the hunt is on... :)

 

 

 

have you checked your fuses?

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GMCanuck Enthusiast

GMCanuck

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have you checked your fuses?

 

Are there separate fuses for the lights running to the trailer wiring? All of the lights are working properly at the back of the truck, but a couple of the contacts inside the trailer connector are dead.

 

If there are separate fuses, where would I look?

 

Thanks.

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