4-pin to 7-pin trailer harness conversion

[Reed]

I’m not capable of doing the work myself so I’ve gotten a couple of estimates to do this conversion. I’ll be pulling a lightweight travel trailer (about 1,000 pounds) and I need to be able to charge the trailer battery while towing. The trailer does not have electric brakes. My Ford dealer gave me an estimate of $400 … UHaul quoted me $90. U-Haul said they didn’t need to run a wire to the engine compartment but can tap onto the wiring for the existing 4-pin assembly. Is that correct or are they missing something? Thanks!

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[DonImbimbo]

The 4 pin has GND - Stop/Right - Stop/Left - PARK

My guess is they will tap into the parking lights for a trickle charge.


The Ford 7 pin has all the above plus: Left Park - Right Park - STOP.

 

[Reed]

The 4 pin has GND - Stop/Right - Stop/Left - PARK

My guess is they will tap into the parking lights for a trickle charge.


The Ford 7 pin has all the above plus: Left Park - Right Park - STOP.

I’ve seen several threads where they run an extra wire directly from the BS battery … which is a lot of work … but wondering whether this would result in faster charging of the trailer battery?

 

[wireman]

I’ve seen several threads where they run an extra wire directly from the BS battery … which is a lot of work … but wondering whether this would result in faster charging of the trailer battery?

It should but would need to be fused close to the battery.

 

[NMhunter]

Many tow vehicles are set up to charge the trailer while driving. They don't charge much, and many people run separate wire for charging.

IMHO, a better system is to put a solar panel with a charge controller on top of your trailer. It charges your battery while the trailer isn't being used, while towing, and while using it. I bought a flexible one, and glued it on with silicone caulking. Lots of information on the web about how to hook it up. Renogy has a flexible kit for $169. It is pretty much plug and play, and comes with directions.

 

[Reed]

I travel a lot in hot, desert environments. And so while I’m on the road, my fridge is using my battery capacity. I also have portable solar panels, which I pull out when I get to my campsite so that helps. But I’m not ready to try to mount solar panels to my roof … could happen down the road. For now, I think I need to be able to charge while I’m driving.

 

[NMhunter]

For running an electric refrigerator, you'll want a DC-DC Charger. Renogy makes one for $159. You will need a heavier wire from the battery back to your bumper.

Log in to Forest River forums and do a search, and you'll learn more than you wanted to know about how to keep electric fridges cold on the road.

Or, you could just put a frozen milk jug in the fridge.

 

[Wandering Pinto]

I converted to a 7 pin for my small travel trailer. I ran a fused 10ga wire underneath directly from the battery for the charge wire. Simple and straight forward.

 

[Ksnau]

I did a post how I did mine for my travel trailer you absolutely can do it yourself please try it's worth it saving money and learning although $90 is cheap or if it's just to charge the battery a small solar panel could do it. I have a 190 for my trailer that does wonders. And for a real 7 pin or real power yes do battery, or that's what I did. It's not hard. I hate doing wiring and electricity stuff and I did it. Also if u do power you'll need a diode to stop the back feed to the baby bronco I used the Roadmaster I forget which model but it's in my post how I did mine and wired everything.

 

[Me3]

Are trailer wiring connectors standard? I have never used a trailer. So if I rent a trailer from U-Haul or anywhere else will the connections match up?

 

[Wandering Pinto]

Are trailer wiring connectors standard? I have never used a trailer. So if I rent a trailer from U-Haul or anywhere else will the connections match up?

The two most common ones used today are the flat four, four terminals for lights and ground. 7 pin round RV connector that adds brakes, 12 volt power, and an auxiliary terminal. I now have both in one receptacle on my Bronco Sport. There are adapters to go between both for light functions

 

[Me3]

Ok thanks. I’ll have to see what the factory hitch came with, but sounds like adapters can make it work. I appreciate it.

 

[Jmuns]

Ok thanks. I’ll have to see what the factory hitch came with, but sounds like adapters can make it work. I appreciate it.

4 pin (4-way flat) is what it comes with

 

[wireman]

4 Pin To 7 Pin Adapter Wiring Adapters Trailer Wiring | etrailer.com

Etrailer a great source for towing and wiring.

 

[timg]

Check the following on Thingiverse for a bolt on, sturdy mount for your 7-pin plug: https://www.thingiverse.com/thing:7041899

If you don't have a 3D printer, or one big enough, you can have it printed by online companies for a small fee, or some libraries now have 3D printers you can use.

I designed it and have been running it on mine for about 6 months in front of my popup camper.

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