trailer wiring

[hntngkd]

Looking for some help with my 7 pin wiring. Hauling a 40ft gooseneck with hydraulic brakes im not getting power to the hydraulic pump on the trailer. I believe it gets power from the aux power wire in the 7 pin, which for my 06 (maybe others too) is dark blue i believe. Im not getting power to it in the plug or the connector right before the plug. Having a hard time pinpointing which fuse it would be linked to as well. Hauling a trailer with electric brakes is no problem but i found out real quick that a 40ft trailer is a hassle to stop without trailer brakes.

 

[Mikey52]

What brake controller are you using? If it's the factory controller, it will not work with electric over hydraulic brakes. Because the electric part has no resistance to start with the controller doesn't know it's hooked up to a trailer with brakes. Most early aftermarket brake controllers will not work either.

The factory controllers for I believe 2016 and up will work.

You can wire in an old brake magnet to trick it into working as this is what supply's a slight resistance to wake up the brake controller.

From your profile the engine is listed as lbz, but not sure what year model truck you have.

Also on newer trucks that will work with the EOH brakes, if the truck is not moving, pressing on brake pedal will not activate the brakes. This is so it doesn't run the pump all the time while sitting at red lights. It will work with the manual squeeze buttons.

 

[M.A.M.]

Blue wire is the brake wire. The power wire should be either red or black. You need a constant power to the pump, and the blue wire will activate it.

If you know which wire is your ground wire on the 7 way connector, the power will will be directly opposite it. So it you have negative at 1 o’clock, power will be at 7 o’clock, and vice versa.


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[2004LB7]

I put a resistor on mine. I think it is 2 ohms 50 watt if I remember right. wired it on the trailer so if it loses connection or something happens it will alert me

 

[Ron Nielson]

https://www.etrailer.com/Accessories-and-Parts/Titan/T4845900.html

 

[dndj]

Blue wire is the brake wire. The power wire should be either red or black. You need a constant power to the pump, and the blue wire will activate it.

If you know which wire is your ground wire on the 7 way connector, the power will will be directly opposite it. So it you have negative at 1 o’clock, power will be at 7 o’clock, and vice versa.


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Yup. Power wire in the trailer connector should be red on the GMT-800 trucks. Power for the +12v terminal in the trailer connector comes directly from the STUD #1 40A maxi-fuse in the fusebox under the hood. Always hot, not switched.

 

[1FastBrick]

Blue goes to the brake output on the controller according to this. https://www.etrailer.com/p-etbc7.html
Yellow In the center spot should be the AUX Your looking for.

 

[dndj]

Blue goes to the brake output on the controller according to this. https://www.etrailer.com/p-etbc7.html
Yellow In the center spot should be the AUX Your looking for.

Blue, correct. Confusing as hell as GM labels it "Trailer Aux Supply Voltage" when it's really the electric brake wire. Yellow wire is left turn/stop. Center terminal is backup lamp supply.

From the FSM.

 

[1FastBrick]

Blue, correct. Confusing as hell as GM labels it "Trailer Aux Supply Voltage" when it's really the electric brake wire. Yellow wire is left turn/stop. Center terminal is backup lamp supply.

From the FSM.

Yeah, I couldn't find my FSM right now. I just got back home from a service call.

According to the other thing I post though, that center spot in the middle should be the AUX circuit that ties into the Hydro brake pump. Of course it's an aftermarket plug so it had 2 yellow wires. One ties in as you described and the other is in the center pin.

Thanks you for posting the FSM info.

 

[hntngkd]

What brake controller are you using? If it's the factory controller, it will not work with electric over hydraulic brakes. Because the electric part has no resistance to start with the controller doesn't know it's hooked up to a trailer with brakes. Most early aftermarket brake controllers will not work either.

The factory controllers for I believe 2016 and up will work.

You can wire in an old brake magnet to trick it into working as this is what supply's a slight resistance to wake up the brake controller.

From your profile the engine is listed as lbz, but not sure what year model truck you have.

Also on newer trucks that will work with the EOH brakes, if the truck is not moving, pressing on brake pedal will not activate the brakes. This is so it doesn't run the pump all the time while sitting at red lights. It will work with the manual squeeze buttons.

The truck is an 06, the controller is a tekonsha prodigy, it was in the truck when i bought it back in 2013, but looking it up that seems like it could be the issue. The newer version says specifically it will work with EOH brakes. This one says nothing about it.

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[hntngkd]

Alright so we had 2 issues, 1 being the controller wouldnt work with EOH brakes. The 2nd being there wasnt a fuse in the stud #1 location under the hood. I pulled the fuse from my abs and placed it there with the new controller installed and held the manual control full left, the pump kicked on. Just to verify that i couldnt use the old controller i left the fuse installed and then switched back to the old controller held the manual control to the left and the pump did nothing. I appreciate the help! Were good to go!

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[dndj]

Cool, thanks for posting back on how the solution worked out and glad you got it working. GM states in their official upfitter guides that the STUD #1 40A fuse is not populated from the factory. It's direct connect to the 12v battery though, so it's possible to draw the batteries down if you leave a trailer with current draw plugged into the truck for extended periods while the truck isn't running.

 

[hntngkd]

Cool, thanks for posting back on how the solution worked out and glad you got it working. GM states in their official upfitter guides that the STUD #1 40A fuse is not populated from the factory. It's direct connect to the 12v battery though, so it's possible to draw the batteries down if you leave a trailer with current draw plugged into the truck for extended periods while the truck isn't running.

Good to know!

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