Hey guys, Thought you RV guys might know the answer here,,One of my hobbies is RC Model airplanes, I built a extension harness that takes power from the 7-pin connector so I can use the 12v. for my charging equipment at the field. This works perfectly on my '02 2500, but I can't get it to work on my '04 suburban I recently bought. I've tried engine running, ignition on and off, I don't get power back there, The 30a fuse is good and in place for the aux tab that powers the trailer harness, What am I missing? Thanks

Did you put in the maxi fuse under the hood? Is the ground ok at the 7 way?

corrosion: first thing I would check for. I've had to plug in and out several times (and improving continuity by scraping) these connections before.

stew47 wrote:Did you put in the maxi fuse under the hood? Is the ground ok at the 7 way?Fuse is OEM 30aLights and brake controller work fine,, so I'd say yes.

JPeyton wrote:corrosion: first thing I would check for. I've had to plug in and out several times (and improving continuity by scraping) these connections before.Tried that, contacts are pretty clean, My Buddy at the flying field has a '06 Suburban, same issue when testing it on his truck

When I got my 2010 Ford truck it did not have 12VDC at the 7-way connector as well. Then I found an unmarked envelope in the glove box that had a fuse and relay in it. No other information whatsoever.Scanning through the truck manual I found mention of TRAILER CHARGE or something like that and it identified a fuse holder and a relay spot in the main fuse panel under the hood.. Turned out this was the place where the items in the envelope were to be installed. With these two items installed then I had 12VDC on BLADE 4 of the 7-way connector when the ignition key was turned ON.Roy Ken

'04 Suburban (power at the trailer connector) | Good Sam Community

BurbMan
Explorer II
May 28, 2015
Now you can tell your buddy with the 06 LOL! Glad you got it working!

The description of Stud #1 in my 2001 owner's manual is a little clearer:
TReiner
Explorer
May 28, 2015
Well I guess when I saw "do not install fuse" I figured I wasn't supposed to put a fuse there period!! It did have the blank plug in there.

Tested it with the 30a fuse from stud#2, Walla, 12v at the plug without the ignition on,, Perfect

Thanks for the help guys

T
BurbMan
Explorer II
May 28, 2015
Assuming you don't have dual batteries, I would install a fuse in Stud #1 and see if that does it.
TReiner
Explorer
May 28, 2015
tnx, but a 30 amp fuse is already installed in Stud #2, I have the factory wiring harness for the Tekonsha Controller installed, as mentioned brake controller and lights work fine, just no 12v at the trailer connector plug
BurbMan
Explorer II
May 28, 2015
Sorry my info was not accurate. In 2003 they made a bunch of changes so the 03-07 models have some significant differences from the 00-02 models.

I found this in the 2004 owner's manual, you want to install the maxi-fuse in STUD #2:

If you want to connect a trailer brake controller, use the harness provided for that purpose:

Here is the harness, GM part # 15085418...be sure to use the right one, the connector is the same as on the 00-03 models, but GM changed some of the pin locations in the connector.
TReiner
Explorer
May 28, 2015
My manual says stud 1 is for "auxiliary power (single battery and diesels only)/ dual battery (tp2) do not install fuse

I'll check all suggestions thanks
wnjj
Explorer II
May 28, 2015
BurbMan wrote:
There are TWO fuses. One is for trailer lighting and one is for the charge circuit. Look in the underhood fuse panel for "Stud 1", there needs to be a 40A maxi fuse installed. Don't eyeball it, pull it out and check it, because they shipped with dummy blank fuses.

Interesting note about the diagram above, the upper left is correct, but the upper right is NOT, because look at where the slot in the connector is. Same on the bottom, the left side is correct but the right side is not.

Here's a pic I like better:

ALSO on the Burbs, the center pin is wired to get 12v when the back up lights come on.

I think the diagrams are fine. The slot in the bottom of the connector is for indexing the connector into the housing. The one on the top of the housing is for indexing the plug into the vehicle socket. They are different genders even. If you look close at the pictures on the right, the wire colors are molded into the plastic.
mbopp
Explorer
May 28, 2015
I had to connect the ring terminal to stud #1 on my '04 Envoy along with installing the maxi-fuse. The terminal was tucked into the wiring harness. I needed to buy a 6x1mm nut for the stud.
Iraqvet05
Explorer
May 28, 2015
Not sure about the Suburban but some years of Silverado only energize that wire when the tow/haul button or lights are on.
BurbMan
Explorer II
May 28, 2015
There are TWO fuses. One is for trailer lighting and one is for the charge circuit. Look in the underhood fuse panel for "Stud 1", there needs to be a 40A maxi fuse installed. Don't eyeball it, pull it out and check it, because they shipped with dummy blank fuses.

Interesting note about the diagram above, the upper left is correct, but the upper right is NOT, because look at where the slot in the connector is. Same on the bottom, the left side is correct but the right side is not.

Here's a pic I like better:

ALSO on the Burbs, the center pin is wired to get 12v when the back up lights come on.