Hello,

I recently bought a 13 foot 1983/84 U-haul camper. I'm trying to get the electrical going, there are two red wires run under the frame (one's grounded) and they come up inside near the battery. Are these intended to charge my deep cycle batteries while driving? If so where do they attach to the flat four, and which wire goes to which terminal. Additionally, do I need a certain kind of battery or will any deep cycle marine battery do?

Thanks
Josh S.

You'll want to research the pin outs for the flat trailer connector, but I don't believe the 4 pin connector has a battery connection. I believe it just handle left, right and stop lights with a ground.

One of many sites with wiring diagrams

Sounds like you've got some nonstandard wiring there if there are two red lines and one of them is to ground.

Flat -Four only runs ground, turn, brake and running lights. You have to move to a six or seven pin connector to get brakes and battery charging.

For standards sake, I recommend using the Seven-Pin Pollack/Bargman connector with the six flat pins and one round pin -- This will also allow the addition of backup lights or a rear floodlight for campground setup.

You asked more questions than you thought. I broke the pertinent information out so we could examine the facts.

1. The fact that you have a UHaul can point to significant clues if you know the differences between your trailer and others. You also need to know the similarities.

How is your trailer similar?
A 4-pin flat electrical connector is a standard fixture on small trailers. It connects the trailer's Tail Lights and Side Marker Lights to the tow vehicle's tail lights and side marker lights. NOTHING MORE than that. The connections are:
White = Tow vehicle's "ground", (or Negative return).
Yellow = Left Turn Signal & Left Brake Light
Green = Right Turn Signal & Right Brake Light
Brown = Running Lights, (Tail and Side Marker)

To do more than that, you need more pins in your connector. A 5-pin flat connector has all of the above plus:
Blue = Trailer Brake Controller Output
This is common for a boat trailer or horse trailer with electric brakes.

At this point, the electrical connectors switch from flat to round. You can also get 4-pin and 5-pin round connectors. A 6-pin round connector has all of the above plus:
Black = House Battery Charge Line (+12 volts)
This is the line you were expecting to find but your trailer does not have.

There are also 7-pin round connectors, but I won't go there this post.

2. How is your trailer different?
UHaul Trailers were designed and built to be short term rentals for regular people. They had to be designed to survive treatment from people who did not tow a travel trailer very often. Therefore, they had to operate pretty much on their own with minimal training.

"there are two red wires run under the frame (one's grounded) and the up inside near the battery. Are these intended to charge my deep cycle batteries while driving?"

I am assuming that these are extra wires, and not the wires that power up the "house" lights and water pump (if you have one). You assumed that they were supposed to connect to your tow vehicle. But they cannot with only a 4-pin flat connector. If they "Come up near the battery" and "one's grounded", where does the other one go to? That is the $64,000.00 question. I would suggest you look on the roof.

Why the roof? Because UHaul installed a 12volt evaporative cooler and a solar panel up there. It would be the solar panel, and not a charge line from the tow vehicle, that would keep the house battery charged up. No fuss no muss for the customer renting the trailer. Minimal down time for UHaul.