I know this is an old post, but I spent most of a day trying to trace all this wiring.
First of all, I have a 2023 Jayco Wren caravan running a Lithium battery and a J35 BM Pro battery management system, but Jayco still use the same wiring connections.
The Pink and White wires on Pin 9 and 10 are connected directly to the fridge and NO WHERE ELSE! On your vehicle, 10 (white) needs to be grounded and 9 (pink) needs to go to either the vehicle battery or your vehicle back up battery. Note that fridge will flatten your vehicle battery in a few hours if you park for a while (found out the hard way).
The black wire on Pin 2 (7 pin side) is indeed the battery in van CHARGING WIRE, and goes under the van to a mash up junction point under the floor near the fridge. From there it splits into 3 wires. One goes in to the Electric Brake wiring harness. No idea why, unless its for breakaway brakes that the Wren doesn't have, but doesn't make sense as if the van broke away there would be no power to supply the brakes anyway.
Another goes into the rear light wiring harness. No idea what for as there is nothing back there to power from the battery, unless its for Jayco Reversing Camera.
The third connection goes to the "AUX" 12V Charging input of the J35 Battery Management System.
The reason I was studying these wires is that on previous vehicles I have used Pin 2 of the 7 pin Trailer connection (normally described as Aux or Reverse Lights) to power a Reversing/Rear View Camera, and wanted to replicate this on the Jayco.
Note, the method detailed here could also be used to allow pin 2 to be used for reversing Lights.
The reason that Jayco separated the fridge and the rest of the caravan wiring, was to stop the caravan fridge from flattening the caravan battery. With the battery management system installed on later vans, this is not possible anyway. Power goes from Pin 2 to the battery and not the other way.
So, I cut the black wire at the junction point underneath the van just before it split into 3. I then run a wire from the back of the fridge (pink wire) connection through a small hole in the floor to the 3 way split side of the cut black wire under the floor. Original connections are now restored and battery will charge from tow vehicle.
Then I was able to use the cut black wire coming from the 12 pin plug to power my reversing camera.
This forum and others was how I found out my caravan battery wasn't charging from my vehicle over the 3 times I have taken it away. Thank god previous owner had installed a solar panel on the roof.
Hi
@iarmstro and welcome to the forum. There are many different ways to wire up your van, but IMHO, you have made it hard for yourself.
Firstly, wires pink and white (pins 9 and 10 ) carry the heavy current between tug and van are are
meant to be connected directly to the 12 volt inputs of fridge (and nowhere else!!) Electrical separation from the tug battery (when vehicle engine NOT going) is usually effected with a manually inline switch or can be automatically disconnected when connected to ignition line with relay, or fridge switch, or a voltage sensitive relay in positive line between tug battery and fridge. That way, when motor is not going, power between tug battery and van fridge is cut off and fridge cannot draw current and flatten tug battery. As there are
two wires involved, the active one to fridge is pink and the earth return to tug battery is the white one. No need for a separate earth!
Other pins on 12 pin plug are as follows: 1. LH turn signal, 4. RH turn signal, 5 van brakes, 6 Stop lights, 7. Rear clearance and side marker lights. Pin 3 provides the earth return for all these lights.
Now pin 2 which was normally used for reversing lights but has been sacrificed to direct power to the tug charging system your J35 Battery Management System. To keep the reversing lights on tug, it is best to run a separate line from tug battery (after cutoff relay) to pin 2 at rear of tug to provide a separate power line to your van charging system and keep the original wiring for the tug reversing lights after disconnecting from pin 2.
Pin 8 is battery pos from tug and can be used for other lights on tug, as can pins 11 and 12, . the common earth return pin 10 can provide the electrical earth return to tug. Remember, pin 3 is also earthing the lighter current from the other lights as well.
I doubt that there is a common positive wire to van brakes and lights as these are separately connected through pins 1, 4, 5, 6 and 7 with pin 3 as the earth return. There may be a line (positive) from from the 3 way split for a separate break-away system for a small battery and to power brakes in the event that van connection with tug is severed. You are correct in saying not needed for your van, but necessary for larger vans, but it appears that Jayco are using a common loom type. I have a similar connection available on my 2013 Penguin and not used. In the past, power from van battery input was prevented from drawing current from tug system because there was a power diode on the input line (through pin 2) on earlier models, but later models with the J35 system have a one way relay to do this. I hope this clears up any doubts you may have had and confirms other thoughts you had.
