TheSamba.com :: View topic - 7-pin Trailer Wiring

Thu Jun 18, 2020 6:50 am

I just picked up a new camp trailer for the summer and it came with a 7-pin wiring harness. I already have the flat 4-pin setup, but would like to add the reverse lights and battery charger.

Any suggestions on where to get the power for the battery? I was thinking straight from the alternator?

Also wondering if anybody has mounted a 7-pin, where did you put it? Might attach it to the fiberglass bumper somehow.

Here is a pic of me picking up the trailer.

And a YouTube tour of it.

Thu Jun 18, 2020 8:56 am

Straight off the Alternator is a convenient spot and assuming the rest of the Alternator harness is up to par, you will be fine.

Thu Jun 18, 2020 9:30 am

I agree that the alternator would work fine, but if you used the power terminal in the firewall wiring distribution box. (Driver side) then you could neatly tie into all of the rear lights at the factory 7 pin connector in one place. There is even a spare rubber grommet in the distribution block for a neatly wrapped new trailer harness to pass through.

Maybe increase the gauge of the wire from alt to power post to match the charge wire of the trailer battery.

Nice looking trailer.

Thu Jun 18, 2020 10:00 am

Type in "4 pin to 7 pin adaptors" on Google. There are even videos.

Thu Jun 18, 2020 10:30 am

To get best charging use a dedicated power wire path from the alternator stud and don't share any existing wire path of the Vanagon. I would put a 40 amp relay in the engine compartment, controlled by the alternator blue wire, to switch on the charging power to the trailer harness only when the alternator is charging. Of course use a fuse/circuit breaker. I would prefer an auto-reset breaker, not expensive.

Keep in mind that every amp used in the trailer over all of the voltage wires has to also flow back to the van on the ground wire(s).

Don't be thinking you are going to get much actual battery charging unless you have sufficiently large GROUND and VOLTAGE wire paths to the aux battery in the trailer.

Mark

Thu Jun 18, 2020 10:46 am

I already have a 4 pin to 7 pin adapter, so it is safe to tow.

Like the relay idea a lot, that would prevent the need to unhook the wiring while parked for extended periods of time. They warn it will drain your starting battery charging the camp trailer, so always unhook.

I will hit up thatvwbusguy to see if he can hook me up with the relays and connections.

Plan to always fully charge the trailer battery before leaving and just picked up 160w solar to use while camping. Just hoping for a trickle charge while driving for when we do extended road trips without shore power.

Sat Jun 20, 2020 9:20 am

I have a relay setup coming to use the two wires on the back of the alternator. Basically looks like a hard start relay. Will post pictures of it installed.

For the 7-pin plug mount I found a solution that hangs off the receiver tube itself, think this will work perfectly. No need to drill or cut more into the bumper.
https://www.curtmfg.com/part/58000l

Sat Jun 20, 2020 5:04 pm

When's the last time you changed or even checked your Trans Fluid. That's a lot of extra stress and and I'd want all that old contaminant out before I start pulling a trailer.

Stacy

Sat Jun 20, 2020 6:00 pm

Just had the first rebuild at 137k and added a Peloquin. We will be towing mainly with our GTI (hence the rooftop tent) but plan to take the Vanagon 900 miles to BNNTA if it is still on this year.

Sun Aug 23, 2020 6:48 am

Well the bracket I hoped would work did not due to the size of the 7-pin plug and the odd chain hook on the RWM hitch.

I ordered some other ones to try and came up with an idea of how to attach it. The steel was thicker than I expected so it went into the vice and heated it up with a propane torch to add the needed bend.

With the plug mount attached, you see the final shape.

Some pics of how I attached it to the hitch, no new holes needed.

And here it is in action.

I also installed the relay kit off the alternator to charge the battery, was super simple. And thanks to Jay for providing an excellent plug and play product.

Ready to hit the road tomorrow and do some camping.

Sun Aug 23, 2020 10:25 am

That trailer is AWESOME! Super sweet and SO practical.
Kudos!
: )

Sun Aug 23, 2020 10:32 am

Wiring for trailer lights is an easy task. That also includes taking the time to plan and do it with care.
Some of the Vanagons I have restored or worked on have had trailer lighting added in. All were completed by slicing into the wiring harness at the taillight. None were done with anything beyond cut and splice with PVC coated butt joints… oh, and electrical tape that is peeling off. Not very elegant.
So, to keep the connections WITHIN the OEM junction box takes some forethought. There is not a wealth of room in there for butt connectors and electrical tape! Here is what I did on my own vehicle:
Open the junction box.
Pull out the connectors and focus on the round 7-pin connector for the taillights. To open the connector carefully squeeze and tug or pry the edge over the locking tab. If you break it, they are available but that makes for even more work. I am lazy, so not for me.

7-pin connector pin removal.
On the MALE side (goes to the taillights) the pins need to be slipped out of their sockets. Lisle makes a nifty tool for this, but it does not protrude deep enough, therefore an alternate route is needed. I procured 1/8” aluminum tubing to do it. K&S Precision Metals #5073 is available at most hobby and Ace hardware stores (if you can get a couple sticks of the 1/8” aluminum tubing it gives you grace for when they bend or break). Poke the tubing into the connector so that it goes over the male pin, then EASILY and with a twisting action (easy now…aluminum tubing WANTS to bend and break) press it deep into the socket until the wire and 1.6mm pin are released. The 1/8” tubing unlocks the spurs holding the pin in the socket. Either mark the socket as to what wire went into that hole or leave the tubing in place to denote ‘home’.

Splicing the wires.
With care, take the wire that has the Molex pin and remove about ¼” of the case to reveal the copper wiring. Be careful to not cut or over stress the wires. With the bare spot in the wire, take a mechanics pick to gently find and create an opening in the wire braids. An eyelet of sorts. Now take the proper lead from the trailer wire harness and WEAVE it into the eyelet. You will then create a loop and wrap with the wires. Like a braid or hair extension : )
Once the wires are meshed nice, slip a section of heat shrink tubing over the Molex pin and cover the spice area. Apply heat with care. The splice is now complete.

7-pin connector insert.
The newly spliced wire can go back into the 7-pin connector. But first take care to be certain the locking spurs on the 1.6mm pin are open. Press back into the connector until you hear the click of ‘home’.
Do this for all wires as per the harness. Then tuck everything back into the junction box where the connections are dry and unseen. That’s about all folks.

TO SEE EVERY STEP OF THIS, GO TO MY PHOTOS

Sun Aug 23, 2020 11:41 am

Thanks!

I previously replaced the entire rear lights wiring harness with one from Kyle that already had the trailer plug spliced in.
http://kyleautomotivespecialties.com

The only thing left to do is to wire in the reverse lights. I plan to do that in the junction box this winter.