My truck has a 4 pin and 7pin connection in the rear. I'm having a 2'' receiver welded to the back of my camper and plan on towing a small fishing boat behind the camper, so tandem towing. Instead of cutting open my underbelly and searching for the camper tail light wiring, a thought was to just run the 4 pin wiring under the camper in wire loom and connect it right to the truck. Question is can I have the camper plugged into the 7 pin and also have the boat 4 pin connected at the same time? I always get the ''trailer connected" message when I have either the 4 pin or 7 pin connected but what would happen if both were connected at the same time? Don't want to confuse the truck, lol.

 

The four pin connector should be spliced in the 7 pin so shouldn't be a problem.

 

Just a side note, check your local laws. I'm not aware of any state that allows tandem towing with a conventional bumper pull. I know you can in some states with the first trailer being a 5th wheel. I know that's not what you asked, just trying to keep you out of trouble. Good luck!

 

It is legal in a few states. South Dakota being one of them.

trailer brakes over 3,000 lbs and an overall maximum length are the only real restrictions

your wiring proposal sounds just fine. As mentioned, they are tied together at the truck anyway.

 

I feel this is an excellent question. I feel my truck, 502a, might throw a fit. It likes to analyze my trailer wiring, and I would think in the magical computer, it would sense 'either or'. You could probably connect the 7 pin trailer, than test the 4 pin with a tester. Personally, if you have old school 1157 on rear of trailer, I'd consider tapping into that rather than running and securing wires beneath the trailer. Make sure you keep a good ground throughout. Let us know what the outcome is, and a picture of your set-up

 

If they were separate at the truck they would have to have separate fuses at the panel.

they are run by the bcm so I suppose anything is possible, but if they have one fuse for both the left, right, and running lights, chances are that they are tied together at the plug.

all of the replacement plugs ive seen have one big round connection with about 8 wires going in. That wouldn’t be enough circuits to have everything separate.

I guess as a test you could hook up the camper and park the boat right next to the truck and hook it up with a long extension. Aside from the chassis ground you get through the hitch, it is functionally identical to what you are proposing- assuming that the ground wire at the boat is properly connected.

 

This is exactly what I'm going to do early next week as I have a 6ft 4 pin extension. Boat is grounded properly. I'll report my findings. As for the legalities of tandem towing in Indiana, it is permitted as long as it's some sort of recreational pull such as a golf cart, small boat, jet skis, etc. and as long as it doesn't exceed 65ft altogether. I will be around 4ft longer than that so hopefully LEO won't have a tape measure. I tandem towed with my prior 2 campers for 10 years without issue. As for tapping into the tail lights of the camper, I requested a wiring schematic from Jayco and found that the wires are routed through the roof [to connect marker lights] and after pulling my under belly and looking, I found nothing. Only other option is to pull the tail light assembly and tap into that way but then the wire would be outside because there's no way to route them down from the inside due to the floor construction.

 

That’s pretty restrictive. SD is 75’ total with a 24’ maximum on the second trailer.

 

More power to those who double tow. I have a heck of a time just towing my 24' boat or 28' TT.

 

Yeah Indiana is more cluttered and half the size of SD. Lots more wide open space out there that I wish we had.

It's actually easier than you think. Whatever you tow behind the camper goes where the camper goes with no extra cutoff. You just can't backup till the following trailer is unhitched.

 

Something else I got to thinking about.

possibly a better solution would be to tie your 4-pin into the junction box at the front of the trailer. This would make it a permanent feature on the trailer and keep from having to make two connections when you hook up. Also eliminates any concerns about the truck getting confused.

maybe yours is different, but mine has a nice junction box on the tongue where everything comes together.

if you don’t have one, adding it is a really good way to have it set up. If your pigtail ever gets damaged, you just replace the whole thing and the trailer wires remain unaffected. One of these would allow you to tie as many circuits together on the tongue of the trailer as you would need. I’ve got one on my car trailer and it is super slick. I just used weather proof ring terminals for both the trailer and pigtail. Kind of a one and done solution when done right.





MICTUNING 7 Way Electrical Trailer Junction Box - 7 Gang Trailer Wire Connection Box Weatherproof for Rewiring Camper RV Caravans Boat Light 7 Way Trailer Wire Connectors https://smile.amazon.com/dp/B07QDQRX...ing=UTF8&psc=1

 

Holy cow! That is a GREAT idea! Thank you! Yes, my 7 pin connects to a junction box right there in front. Are the 7 pin wires color coded? It would be very easy to tap into those wires [ground as well?] with the 4 pin then run it back to the back of the camper. I already have a diagram of the 7 pin connector wiring but the wires are in a sheath so that's why I asked if they're color coded. And thanks for the link for the junction box, it looks way better than the one on there.

 

The one I got was color coded and labeled for each color. However none of the colors matched so I had to trace it all out with a volt meter anyway. The junction box mostly matched the trailer wires, but my new pig tail was all wrong. It had all the right colors, but none of them matched what they were supposed to do.

I would make all of my connections in that junction box including the ground unless you suspect that the camper ground is problematic. If that were the case, I would run another ground wire right to the frame and into the JB and have it all connected together inside the JB.

I use heat shrink crimp connectors. Harbor freight is a good source if you have one near you. Just crimp and then use a heat gun to shrink the tail. Makes about the best weather tight connection you can do without going to extremes. Often times I will put some dielectric grease on the bare wire before I crimp it. It just adds that much water resistance to the connection IMO.

If you can’t find heat shrink terminals, just slip a piece of heat shrink tubing (dual walled if you can find it) over a regular connector and it will be just as good.

they do make connectors with low temp solder as well. You just put the wire in there and the solder melts with a heat gun. Those are really spendy though. I’ve been happy using the other, but I think the low temp solder ones are probably top shelf.

 

Thanks again Mike, just ordered the box. I like the multiple exits so I can insert the wire loom for the 4 pin wires into the box for added protection. I think the wires from the 7 pin in my current junction box are just wire nutted to the camper wires. I'm still going to tow the little boat down there and with my 4 pin extension and just touch the 4 pin wire to what I think is the correct wire for each application and see if it lights up, lol. Yeah, probably take my voltmeter too.

 

Great idea, glad that I stumbled into this thread. Thanks!!!👍👍👍