Trailer plug wiring mystery - 12v going the wrong way!

Hi Kev,

Thanks for the reply. I've just tested that pin on the vehicle plug, it's giving out 12v even while the car is off. So it looks like every time the vehicle is plugged into the trailer it is connected in some way to the battery bank in the van. Interesting! I thought this was a bad thing to do without a battery management system (draining batteries, spikes, etc..)

A little confused - but I guess if it works then we'll leave it as is and do without reversing lights.

Thanks!
Dave

Bought the van and the car separate - haha. chances of them been wired the same?

I agree it is most likely a direct power supply to trailer either for lighting or charging a battery in the trailer. Common with dual batteries fitted to tow vehicle. Not a great idea if only one battery in the tow vehicle for obvious reasons.

Cheers
Wayne B

Gooday Teddy : If it was me I would be changing it maybe a separate plug ( Anderson etc ) maybe seek help from sparky !!!!

on another note , when weird thing happen to your lights on a trailer check the earth ,a bad earth does some strange things .

cheers nick

Hi Blueteddy,

When I bought my Jayco Expanda recently, that's how they wired it for me - although in a small, round 7-pin plug/socket in my case. They use the reversing light pins to run power from tow vehicle battery to van battery (and run the fridge while connected). I am surprised it appears to work as the wire size doesn't seem nearly adequate (my van battery HAS been charged though - when I leave the fridge off).

The Jayco salesman reminded me to turn the fridge off if I stopped for a while because it would drain my car's battery (because the wire stays live - as you've found). I couldn't rest worrying if I would forget this and end up stranded with a flat battery! So I had a Redarc installed in that lead to isolate the van once I turn the ignition off - now I can relax and forget about it.

Gavin

My van has an Anderson direct to the battery. The fridge was wired to pin 2 of the van plug and the tug pin 2 wired to the reversing lights. Of course this was unsatisfactory so the fridge was then wired to the Anderson plug wiring and of course pin 2 was then 12v at the van plug and the reversing light on the tug were on whenever the van was plugged in, disconnect pin 2 and all was fine. It seems there are a couple of "standard" ways of wiring vans and tugs.

I haven't got the box with me but I recall that the plug box had pin 2 as 'reverse'. It would appear that even the manufactures are not up to speed with aus standards.