Power at Trailer Plug

KV Bruce

Original poster
Member
Apr 4, 2020
4
Kern River Valley, Ca
Greeting to all. I have a 2005 Silverado 2500. All the trailer lights work properly but I have no power to pin 2, which I believe should charge the battery in my RV trailer while underway. I can not find a fuse for this circuit. Anyone know if there is and where it might be located. Thanks in advance.
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
There should be two red wires that are disconnected and taped up near the fuse box. One is for the B+ to charge the trailer's battery and the other is for the trailer brakes. I know that on my 08 Avalanche, I had to connect both. There should be two posts at the front of the fuse box. Check your owners manual for further details.
 
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Reprise

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Jul 22, 2015
2,724
Here's a picture that I found on Google, showing the underhood fuse center, and the post where the red wire should connect to:

1643500340999.png

Notes:
- When this is active, the charge requirement is *averaged* between the underhood battery and the battery on the trailer, so if one battery is significantly lower than the other, don't expect the logic to charge the one with lower state of charge (SoC) at the expense of the one with higher SoC .

It's also a fairly low trickle-type charge that goes to the rear trailer battery. If you have dual batteries underhood, or multiple batteries on the trailer, then the charge is averaged between all of them.

If you need better / faster charging for the battery on the trailer, you can get a DC-DC step up charger (one example is HERE ; there are others. These come in handy if you have a large battery bank on your trailer / RV, and need faster charging than your truck's system will provide by itself. I don't run one (yet), but I've heard nothing but good things about them.

- While this photo references 'brake controller'... if you're going to run one, the better way to hook it up is under the dash. A couple of companies (Tekonsha is one) make a pre-wired harness that plugs right into the fuse box by the driver's side kick panel, making connection of your TBC a snap (mine even terminates at the other end to a plug that goes right into the back of my TBC).
It's dark as I write this, so if you want a picture of mine, you'll have to wait a bit. Or search online 🔦:laugh:

If you have the owner's manual for the truck, it'll show this connection and detail which fuse goes to your trailering harness.

Finally, the connections can corrode over time at the plug end, so if you've got everything hooked up and still no +12v at the plug, you'll probably want to check continuity at the 7-way connector. You may need to clean up one or more pins (and some dielectric grease helps keep things in check, back there).
 

6716

Member
Jul 24, 2012
821
I had a power issue in my plug and everything checked out EXCEPT one of the pins that goes into the back of the plug was bent and wasn't making contact. I have no idea how that happened. I only found it because nothing else made sense so I started taking the plug apart and found it.
 
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Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
:iagree:

I had a mystery non functional ground pin at the trailer plug on the TB and it turned out to be the plug that plugs into the plug :blinkhuh: . The 7 pin plug has a plug behind it and when I pulled it out, it was full of green corrosion. Some cleaning and corrosion preventive grease fixed it up.
 

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