Would running wires from number plate let indicators and brake lights work?
Good point whitebeach, I think you would only have power and probably only when the 'Park/Headlights' are on.
To get brake and indicator lights you will have to tap into the existing wiring harness, maybe like dogbox says, have a seven pin plug at the back of the van and a male plug from the bike rack lights.
I did what you are asking about on my camper trailer.
I basically took a new branch off the existing trailer light cable for the bike rack.
First I found where the 5 core trailer light cable entered the camper trailer at the front, and cut it. I then wired both ends of the cut cable to a twelve way terminal strip, and added a third cable that runs from there under the trailer to a new 7 pin trailer plug on the rear of the camper for the bike rack to plug into.
As I have LED lights on the camper and they draw so little current that the car doesn't recognise a trailer is attached, at the same time I wired in two power resistors between right and left indicator circuits and negative so that the car would activate it's towing features.
Here's some pictures to help understand what I did.
Twelve way terminal strip ($15 on Ebay)...
Terminal strip wired up inside camper, one cable in, two out.
Wiring diagram....
New trailer plug on rear of camper for bike rack...
Bike rack in place...
I'm sure you could do something similar with your caravan.
-- Edited by Mamil on Saturday 9th of July 2022 11:45:42 PM
If you can mount a connector strip in a covered area, remembering that you need access to the area to do the wiring, do like as suggested above, BUT:
Get a "chocolate block type: strip from Jaycar, follow the same idea without all of the multiples to keep it simple.
For each function:
Feed in from car, paired with feed out to new rack cluster, on one side.
Feed out to installed van lights , paired with one leg of the load resistor if required, on the other side.
The other ends of the two load resistors go to the earth return - if following the colour code it would be white, along with the returns from each cluster.
Jaycar have various size strip connectors to suit the wiring involved. Just carefully strip 12 - 15mm of insulation from each colour, twist the strands together, and insert. Be sure to screw terminals down firm, but not overtight.
Whole strip needs to be held firm against waving in the breeze going over bumps, and kept dry - so a hidy-hole/ cupboard/ box is needed.
Jaycar can supply a water-proof jiffy box and through box side "cable glands" if required. Otherwise, seal holes with a dollop of silicon once all done, tested. Then mount the box in a stone safe place under the van.
Run any new cable under the van in split conduit, or black poly-pipe to protect it. Be sure to run the conduit/poly in a secure manner. Cable ties do give up. Road grit/stones do take their toll.
At the rear of the van, mount a 7 pin round socket. Then a 7 pin round plug with a shorter fly lead up to the cluster on the rack. Just make sure that the fly lead is not too long/ can get snagged. The plug/socket it to allow for easy removal should there ever be a need.
The trick will be to find enough slack in the original cable to make a loop to allow for the connector strip etc.
Wiring for van interior - lights, fridge, battery, solar, brakes, all go un-touched. It is just the running lights being augmented.
