I took a TOW VEHICLE END seven way plug, and modified it like this:

FROM THE 12V connection, I began running jumpers - first to the running light contact.

From the running light contact I added a jumper to the reverse light contact.

From that - I ran two wires.

One goes to a long extension wire (two conductor) with a switch (momentary on) and back to the brake connection.

The other comes out of the connector to a spade connector for a turn signal flasher.

A turn signal flasher is added.

A second spade connector is on a wire going back in from the flasher to the left turn and brake contact.

The left turn and brake is jumpered to the right turn and brake.

What I have now, is a device that can be plugged onto the trailer seven way that will use the trailers own battery to light up the running lights, flash the turn and brake lights, light a reverse light if the trailer is so equipped, and gives me a switch to check the trailers electric brakes.

Diagram to follow...


~Wolfie

PS: I built it to use as a shop tool. Price? About eight bucks, not including wire and connectors.

 

Hoppy's is kind of expensive, but for as much as I use them at work, they were worth every penny.

 

I can build that kind of stuff!

- I was a NAVY electronics tech for twenty years...

Besides, with a SNAPON tool chest as big as I bought - there are drawers I have not even OPENED yet!!!

 

Thanks for the cool tip, Wolfman!

 

You have way to much time to think of something as cool as this .

 

I don't have enough time - that's why I built it...

Instead of using a simple jumper and walking around a trailer 6 times, I can make them all work at one shot, and even test the brakes!

I did it in such a way that no contact has more than two terminals connected, so that it fits in the shell better. Leave the jumpers long - you'll still have to cut out the back of the plug for room. Loop them right on out and back in.

I used spade connectors for the flasher unit so that it can be easily replaced if it goes bad.

 

I'm also thinking of adding a "GROUND TEST POINT" to the ground contact, so I can test for bad grounding.

"Be thorough, it pays off"

 

I don't know how electrically inclined you are, but in my trailer side hoppy box, there is an Ammetre. Its 2 amp per LED, and is very handy for checkling load. It makes it easy to see if one side is pulling more load than the other, or if it's shorting out.

 

I have an ammeter that can be held against a wire to see current draw.

I nabbed it right out of the parts store for dirt cheap!

It's about the size of a pack of smokes cut in half the long way.

 

Install a small pilot light between your 12 volt charge circuit terminal and the ground terminal if it lights up the trailer ground is OK and you have power.

 

Any way you can simulate operating conditions and have test points is a good test rig.

 

How about a picture for us that need visual help?

 

We built a tester for testing the truck side of the towing equation it's just an old metal "briefcase" that we put 7 marker lights and glued 4 magnets inside to simulate a trailer. It's got about an 8 foot lead with an rv plug on it and there's enough room inside the box to store all of our adapters to do cowboy plugs and 4 pins. Pretty cheap compared to those expensive emulaters, But better than the cheapy ones.

 

You could also drop by radio shack and pick up a large plastic project box to mount it all in. Then setup some toggle switches with LED indicators to see what you are turning on. the flasher and momentary switch for brake lights as well. If you really wanted to be fancy setup your ammeter and voltmeter display on the box as well. If it is setup right for 7rv, then with appropriate adaptors you'd have the rest of trailer connectors set. For the flat style you'd need a battery or 12V source. I haven't made one yet but I just might as I have all the stuff to do it. It would make fixing other's trailers quicker. One key point as this would be a test setup and you really don't know what your plugging into. Use a resetable fuse link in the box, a 10A should be more than sufficient but go with what you want.

 

Let's think about what the several connections do.

Some of then you want to be able (with a test rig) to turn on or off. That pretty much says we need toggle switches.

Selectable power from either the RV battery, or an outside source. A cut-off jumper cable works for the connection to a spare battery.

It should be able to select brake lights, turn lights, reverse lights, running lights, and have a potentiometer for a brake signal, or a full-on, full-off toggle switch.

Seems like a simple project to me.