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Wiring questions - Aux and/or 12v

1075 Views 9 Replies 4 Participants Last post by  DL1221
Hi all,
I've got a quick question. I have a 98 12v which has a 7-way in the bed and a 7-way on the factory hitch. All the lights work great, as does the trailer brakes plug (#2). i have no power to the 12v pin (#4) or to the center aux pin.

I am going to be towing my friends travel camper which has 12v battery power for lots of the interior lights. does the trailer charge through the #2 pin, or should I have power to #4 or the center? looking at the wires going in I have the flat 4 plus a thick Black, blue, yellow, and white wire... White I guess is a heavier ground, and i dont know about the rest... just want to make sure we are good to go as its winter and we are heading to canada with the trailer. thanks
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OK, first of all that picture that you have on your post is wrong. The connector on the right is the one that belongs on the "car end," not the other way around. Take a look at this link, it shows all the pins and their wire colors:

TSB 08-33-96

So the number 4 pin (top right flat pin) is the battery (+) power. It should be hot at all times. The wire color is red/tan (12ga thick wire) If its not, check the number 7 fuse again, even though it looks good replace it anyway. I've seen some that look good, but are still bad.

If you still don't have power, then you either have a bad/loose connection somewhere along, or someone messed around with your trailer connector and screwed it up, somehow. If your connector is worn and corroded, this may be your problem, clean or replace it.
Odd that the diagrams are different, but yes my #4 has power! So I'm guessing the #2 pin only has power when the brakes are applied?

Perhaps my truck is working just fine - that would be cool!
Yup, I don't think there's anything wrong with your truck, you were just looking at that wrong diagram.

The #2 pin is the feed wire for the trailer electric brake controller. You need to buy a trailer brake controller and plug it in to the harness under your dash (there should be a plug there if your truck has the tow package). Once you have your brake controller installed and working properly, it will send current to the trailer's electric brakes via this #2 pin. Here is a link that shows some brake controllers, and if you scroll down a bit, you can also see the harness that plugs to the controller and to the plug under your dash ($14.95)

Brake Controller -

You can also read more about the types of trailer brakes here:

Hydraulic Trailer Brakes, Trailer Brakes, Trailer Accessories
so if i have a trailer with a battery it will get charged by the black wire from terminal #4?
Yup, that's the idea.
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