Trailer Wiring 101?

[dieselcruiserhead]

Hi guys,
Trying to figure out the wiring scenario for my trailer.

As we know there are 4 plug (which is non brake) - turn signals, running lights, ground. I guess turn signal doubles as braking, which is weird...

Then there is 6 plug and 7 plug. I'm unsure of what the functions of the 6 and 7 are except I know they have electric brakes in there somewhere. I'm going to google right now to figure out what is what as far as poles and wiring pattern.

I started trying to figure out which one would be best, and which would also be most universal so I could move the trailer from vehicle to vehicle with the least computability issues including loaning it to friends as needed.

I purchased 6 prong stuff yesterday. But it seems 6 prong is less and less common. I started eyeing cars on the highway and nearly every SUV seems to have 7 prong it appears.

Also, how are people who have batteries on their trailers wiring the charging for the battery? Which draw are you using?

Thanks,
Andre

 

[dieselcruiserhead]

Related...
Link: http://www.accessconnect.com/trailer_wiring_diagram.htm

Looks like 7 prong is the way to go if you want backup lights. 6 or 7 prong works for charging a battery or supplying a permanent 12v for lights or power on the trailer I suppose...

I guess I answered my own question...

 

[dieselcruiserhead]

Another interesting link. I'm realizing I may be running into an issue because I wired seperate bulbs for all 4 functions, similar to a Toyota or Japanese car. Which is addressed here:
http://www.marksrv.com/wiring.htm


stop
turn signal
brake
reverse

Looks like most diagrams use a turn signal and brake as the same wire. So braking would prevent a trailer from operating as a turn signal.

Thoughts?

 

[Martyn]

Andre

Wire everything on the trailer to a junction box on the tongue.

Run the lights, brakes, and 12 volt from the trailer to it, and then run the 7 pin plug and cord to it.

It's great for trouble shooting and adding more circuits down the road.

The 7 pin plug is standard these days. The only issue you have is there is no adapter for a vehicle with a 4 pin and a trailer with a 7 pin. The best thing to do is run a 4 pin out of the junction box as well. That way you have a 4 pin and a 7 pin. ( I know people will show pictures of vehicle with a 7 pin and 4 pin socket, but many vehicles just have a 4 pin).

Remember in many States it's illegal to have electric brakes on the trailer that are not hooked up to the vehicle. Which is what would happen if the 4 pin was used.

 

[dieselcruiserhead]

Very good advice.

How about stop lights and separate stop and turn signal bulbs on the trailer? I found this adapter that is somehow able to pull a stop light out of the dual turn signal / stop light feed of 4 plug adapters. But I can't find one for 7 prong.

I'm sure wiring the brake wire would do the trick but I know it's variable voltage going to the electric brakes. But I found diagrams that suggest that's a good way to do it.

And I suppose you're saying ignore 6 prong all together?

 

[Martyn]

I know about adapters for joining separate turn and stop light on the vehicle side, but not the type you are talking about.

 

[dieselcruiserhead]

Sorry, I forgot the link:
http://shop.easternmarine.com/index.cfm?fuseaction=catalog.prodInfo&productID=4992&categoryID=0

 

[dieselcruiserhead]

Here's another one. Notice 4 in and 5 out. Looks like I'd have to wire this in to the trailer to have my seperate bulbs. Will be complicated if I want to use trailer brakes too. So annoying that trailers use this standard, in my opinion, for all of us with Toyotas...

Both of these are from:
http://www.wiringproducts.com/index1.html

One more in the three wire version... I think this should do the trick, just wire it backwards I suppose...

 

[JSBriggs]

those are for adapting the vehicle with separate stop and turn, to trailer combined stop and turn. You cant wire then in reverse. They use diodes to combine the signals without giving 'feedback' to the vehicle. They are a one way gate.

-Jeff

 

[UK4X4]

Just did a similar thing here as my trailer was wired for the us 4 pin,
around here there are no "trailer" stores.

But they do have 7 round pin plugs and sockets for truck umbilicals.

So I added turn lights to the trailer, as previously it was dual function and I could not find any kinky adapters here.

The spare wires on the 7 pin I used for two positives for the second battery in the trailer

I think Martyn probably has the best idea with doing the wiring in the nose box or having a junction box and having two cables.

You can buy male male plugs or make you own if you'd rather female receptacles and not two permanent cables.

 

[fj40fax]

Sorry, I forgot the link:
http://shop.easternmarine.com/index.cfm?fuseaction=catalog.prodInfo&productID=4992&categoryID=0

I had to use one of those when I wired my 40 for a 4 plug so I could pull a trailer with it. I am pretty sure you cannot use them in reverse.

 

[Faramir66103]

Andre

Wire everything on the trailer to a junction box on the tongue.

Run the lights, brakes, and 12 volt from the trailer to it, and then run the 7 pin plug and cord to it.

It's great for trouble shooting and adding more circuits down the road.

The 7 pin plug is standard these days. The only issue you have is there is no adapter for a vehicle with a 4 pin and a trailer with a 7 pin. The best thing to do is run a 4 pin out of the junction box as well. That way you have a 4 pin and a 7 pin. ( I know people will show pictures of vehicle with a 7 pin and 4 pin socket, but many vehicles just have a 4 pin).

Also, this gives you more options and does away with an easily misplaced adapter that you can't live without.

Ages ago, I was on a holiday trip with a buddy, his family and their ski boat. He had one type of connector on his van, and another on the boat trailer and an adapter in the middle. He lost the adapter at some point that weekend and it caused significant trouble for the trip home. With this junction box idea, you eliminate that potential problem and make the trailer more compatible with multiple tow vehicles.

Thanks Martyn!

Adam

 

[dieselcruiserhead]

No you can wire them on both sides of the equation, the trailer and the vehicle. Here are both, next to each other:

EDIT: that's annoying. They keep parsing my link. Type "converter" into the search function and you'll see them next to each other. The description is nearly identical but one is for the trailer side, the other is for the vehicle side. http://www.wiringproducts.com/index1.html


So these are my thoughts, whether to wire in two of these stupid adapters to match the trailer standard to move it between more vehicles, or just wire it straight up as I have to wire at least a few of the vehicles still, and it will at least work perfectly on my vehicles (which are all Toyotas). The other vehicles would lose their stop lights only and turn signal and running lights would work, unless I wired electric brakes into the stop light. But I'm not sure now much electric brakes are knocked down with voltage.

I hope this all makes sense.

 

[Martyn]

Andre

All of the electric brake set up is done on the vehicle side with the controller picking up the signal from the brake light circuit. The controller is then wired back on it's own circuit to the socket at the back of the vehicle.

There is however an other way to do it, but I'm not certain how legal it is in the US. The controller can installed in the trailer and pick it's signal up off the brake light circuit on the trailer side. I've never done it this way, but it is theoretically possible.

If you wire it this way you have to pre-set the controller based on the weight of the trailer and for highway or off road speeds.

 

[dieselcruiserhead]

Interesting.. I have to say the whole trailer wiring / technology / adapters thing really wreaks to me of just a serious lack of practical standardization. It really is a mess...