Hi everyone I’ve just bought a 67 plate superb estate with a Westfalia detachable Towbar and 13 pin swing out socket, when I’ve plugged my universal bulb tester there is no audible noise to tell me that my tester is connected, and when I turn on the lights or an indicator the tester is still showing red and it should be green! should it show up on the dashboard that a trailer is connected or is there a setting that has to be adjusted via the infotainment system?

Do trailer lights work when they are plugged in?

 

I believe that the 13 pin socket needs 2 pins of the trailer plug to be linked together to create a circuit when its plugged in, are you using a 13 pin tester or a 7 pin one with an adaptor?

 

In either case it would need the 2 contacts linking.

 

Others have said that on the 7 pin dedicated wiring set up the trailer control module detects the resistance of the trailer bulbs, if yours uses that type of sensing then I would not expect a tester to work, they only draw the minimum of currect to light the LEDs and the trailer control module would not be able to sense that one had been plugged in.

 

In many ways I am glad to have simple non dedicated trailer electrics, I dont have reversing sensors etc and my tester works just fine.

Thanks for replying haven’t tried it yet only picked the car up this afternoon, hoping it’s something so so simple 

Sorry a 13 pin tester my caravan is a 2020 model

My electrics are non dedicated 

I would first test with a trailer/caravan/trailer board connected, if you have no lights then I would check the live feed and perhaps the earth to the towing socket relay, mine had been hardwired very messily to the battery with some dodgy crimps, not knowing what it was and not being able to trace where this large current wire went to I disconnected it in the hope of finding what did not work, this was on my previous Octavia where the PO had had a so called specialist fit a towbar.

 

It was only when I came to tow and got the same result as yourself it dawned on me what I had disconnected, I reconnected it using proper terminals and a fuse to the a free terminal on underbonnet fuse box bus bar.

 

Somebody may have done the same to your vehicle of the fuse may have blown where shorted trailer wiring has been connected.

Many thanks where can I find the suspect fuse? Is it in the wiring loom or on the wiring  to the 13 pin?

I am assuming that as its not what many refer to as "dedicated towing electrics" that there will be a multiple relay module triggered by a small control current from the rear lights (it also gives an audible signal when the trailer indicators flash), this will probably be located behind the LH boot side panel, the main feed wire to that will probably have an in line fuse, you will have to tace where it goes, it could be to the rear power socket, to the dashboard fuse box or direct to the battery.

Hi there I’ve tried the 12v rear socket that works ok what colour is the relay?

Hi there Where can I find the control box?

 

From what you've said, it's a non-factory install so it could be anywhere! It depends where the fitter felt like that day

 

The colour is probably black based on a google search for bypass kits, it could also be clear green colour. It'll depend what's been fitted.

 

Obvious first places would be behind the side panels in the boot or around the wheel well.

 

Given you've only just bought the car, I'd be tempted to take it back to the dealer to have it checked out...

14 hours ago, J.R. said:

 this will probably be located behind the LH boot side panel

 

Many thanks, I will give it a look thanks to everyone for all the advice and guidance.

 

I love being a part of this forum 

The best way is to trace the cable back from the socket, if you lift the boot carpet you may see it, if its been done in a half decent manner then you wont as it will be tucked behind the rear trim but if you tug back & forth on the exposed part of the cable from the socket to the rear panel you will probably hear whether it goes left ro right & might see something else moving.

 

My money is on it being behind the LHS boot trim, often when the washer pipe freezes and comes apart the fluid goes over the relay and gives it the good news.

All sorted now many thanks