Need suggestion for trailer wiring

On my GM truck, there's a "camper wiring" option that allows a 7 pin to be installed in the truck bed. GM has had that camper wiring package for 20+ years. All it consists of is a Y harness off the main trailer wiring harness, which is routed back forward on the truck frame and ziptied from the factory.... at leas up through 2014 that's how it has been. 2015 an newer might have a plug in the bed from the factory - I don't know since I haven't truck shopped GM since buying my 2009 in 2009.

Essentially that "camper wiring" package is similar to the Torklift Y harness, but it integrates with the OEM wiring connectors under the truck.

The 7 pin wiring is woefully inadequate for charging. I found this out and upgraded

Here's my project video

To consolidate replies, let me first state that I never mentioned having a 4-pin connector anywhere in the scheme of things. All I said was that I had seen a 4-pin splitter for sale but not a 7-pin splitter. Kayteg1 was nice enough to provide a link to one that is available. Personally, I always try to do the easiest thing first and was trying to avoid creating any separate wire harnesses or creating a second connector myself (not my strongest skill set). The link that Kayteg1 provided is quite likely all that I'll need. I also realise that the 4-pin connector doesn't have a 12VDC output for charging and have in the past used one to connect a small utility trailer (with no battery or charging requirement) while also using the 7-pin for the TC. Again, thank you all for your input and help :-)

Grit dog wrote:
Buy or build a 7 pin splitter pigtail. I bought one from Torklift, because it was reasonably priced, but not terribly difficult to make either.
I've not seen mass produced ones for sale. Torklift one was made in house.

I built one for my SuperTruss. Off the rear male connector going to the truck, I have split a female end that plugs into my truck camper cord and a second female connector at the end of my truss for the enclosed trailer.





I also have run heavier gauge cable to share power between truck, camper and trailer where you see the 2-contact red plugs.

A 4 prong flat trailer plug does no have 12+ battery . LT/brake , RT/brake , running lights and ground .

Buy or build a 7 pin splitter pigtail. I bought one from Torklift, because it was reasonably priced, but not terribly difficult to make either.
I've not seen mass produced ones for sale. Torklift one was made in house.

So, your question was that you have a 7-pin on the truck (all wired correctly with 12 volts at the #4 pin) and your cargo trailer has a flat-4 plug?
The adapter will work, should work. Make sure you have the 12 volt wire on the flat-4 actually going to the battery and that the fuse is good. **oops, no charging voltage in a flat-4** edit.

To get a better charge, if needed, to the trailer battery you can run a second plug using a 2-pole (or even a 1-pole) plug and socket using much heavier gauge wire than the little plugs offer.
I run a 2-pole with positive and ground as the two with finger-sized wire. I run that off of the starter motor 12+ connection (it is closer than the battery/alternator and not being used while driving otherwise). On top of that it is controlled via a solenoid that I can turn on or off at the dash.

Kayteg1 wrote:
My Ford has dual trailer plug, so when I pull utility trailer, I plug it into 4-pins when camper plug goes into 7-pins.
You can make an adapter like that if you don't have it.
For both 7-pins Here is ready adapter.

This is exactly what I was looking for ... thank you so much. I found 4-pin splitters like this but I couldn't find a 7-pin like your link shows. And yes I do have a good 12 volt source at the Aux pin in the connector. Thank you all for your help.

Using factory wires it is good idea to recheck ground wire on older truck.
I had F350 that was giving me intermittent charging problem and after long search I found heavy ground wire going 1/2 length of the bed under and bolted to the frame. The 3/8" bolt gave it bad connection and that was on CA truck with no corrosion.
You will get some ground connection via ties on camper, or via hitch on trailer and that adds to hard troubleshooting.

First off, have you verified that you have 12 volts to the aux pin?
Many manufacturers dont have the fuse in place to energize that wire.
Check the voltage before modifying, it wont be a lot, but you should get some charging even with the existing small wiring.



Also if you do decide to increase the wire size, verify that you have at least the same size ground lead.