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I've got an 09 3500HD Dmax 4x4 SRW and the dealer I bought it from didn't hook up the aux battery feed wire that charges the trailer batteries. The "book" says have the dealer do it, but it's just a wire off the main harness with a terminal attached . Anyone out there done this themselves?

Thanks

Dave
 

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There are two red wires by the fuse box under the hood. Each are labeled to what they are and rolled up up. Next you are to attached to the studs on the front side of the fuse block when the cover is removed. But what I am not sure is if the fuses that are there are real or dummy fuses. May have to get some 40amp fuses for those locations. If you have a meter test to see if 12volts is on the stud to ground.

Brian
 

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I just picked up my new 09 2500 Duramax yesterday. Today I checked to see if I had 12 volts at the trailer plug on the truck to charge the battery on my travel trailer--did not have 12 volts for charging, however the lights and turn signals worked. Under the hood the wire near the master cylinder was already connected to the stud on the left as you face the engine compartment from the front of the truck. The other wire next to the fender was not connected to the other stud, so I connected it. The fuses were already in place and I have 12 volts at each stud--however I still do not have 12 volts at the female plug for charging the trailer battery--oh well I'll check more tomorrow or it's back to the dealer. Any suggestions?
Thanks,
Ron
 

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what you think are fuses, are blanks. pull them and look at the underside. I would bet there are no metal contacts.
 

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I didn't pull the fuses, but I am getting 12 volts at each stud where the wires are connected so I figured the fuses are good. It seems to be somewhere between the studs and the female plug at the end of the truck. This truck has the intergrated brake control, but I would think that the 12 volt power supply to the trailer plug would be separate and just go straight to the plug. I may need to check the plug itself and the wiring in between--or I could just let the dealer do it.
Thanks for your input.
 

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If you connected the wire correctly and have power at the stud sounds like a warranty issue to me. I would double check your connections under the hood and meter the plug again. If you still have nothing I would let the dealer look at it.
 

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Well the problem with not having 12 volt aux power at the rear plug of the truck is solved.
There are three wires on the 2009 Duramax 2500 for integrated brakes, after market brakes, and 12volt aux power.
The truck came with integrated braking, so one of the wires from the bundle near the master cylinder was already attached to the Larger stud at the underhood fuse box. There is another wire in the bundle near the master cylinder for the auxillary 12 volt source. That wire goes to the smaller stud, 6mm. Both 30 & 40 amp fuses were already installed in the truck. The third wire next to the left front fender is for an after market brake controller. If you install an after market brake controller, you disconnect the integrated brake control wire from the larger stud and put the third wire there.
I am now good to go.
 

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Thank you for your post, I just figured mine out, there are actually 3 wires, I just assumed the big one coming hooked up was hooked up by the dealer and on the wrong post(which actually makes no difference). I looked a little harder for the third wire and it is the one everybody is talking about. I now have juice back at my plug. Should save me a few dead batteries on my trailers. Thanks again
 

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Yeah, how long would it have taken at the factory? 2 seconds? :)
 

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I have read all the helpful info but need to know if the info on the 2009 auxillary wire hookup would be the same on my 2006 duramax 3500 dually
Thanks
 
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