Towing electrics - no brake lights

[StevenH]

T6 Kombi van 2018 - converted to full camper. Just noticed a problem when towing my caravan, the right indicator isn’t working and instead flashes both brake lights on the caravan. The brake lights don’t come on when depressing the brake pedal.

I bought one of those cheap towing electric testers from Amazon and it shows a problem on the T6 with the brake output.

It’s a towtrust detachable towbar but not sure if it’s genuine loom or relays. I also noticed that the repeater audio (beep) is not working on right indicator. Has worked perfectly previously.

I’m currently on holiday in the Isle of Wight so would appreciate any advice and/or a local vehicle electrician that could take a look for me.

 

[Deaky]

It will be a bypass relay. OEM factory wiring has no beep

 

[StevenH]

It will be a bypass relay. OEM factory wiring has no beep

Yes I think that’s likely. I only paid £500 installed.
Where would I find the bypass relay?

 

[Deaky]

Yes I think that’s likely. I only paid £500 installed.
Where would I find the bypass relay?

Probably behind one of the rear light clusters

 

[manfrotto]

Have you tried a different trailer, in case the issue is the caravan (eg bad earth etc) not the van wiring?

 

[StevenH]

Have you tried a different trailer, in case the issue is the caravan (eg bad earth etc) not the van wiring?

I’ve tried both the caravan and the Amazon tester.

That being said I do think it’s a bad earth. Going to get a multimeter and test the earth.

 

[The Bear78]

Have a look at the wires going into the back of the plug. If it isnt sealed up and water and muck has got in it will make a mess of the connections which are often poor quality.

 

[StevenH]

Update. Earth seems fine as tested against left indicator and side lights.

No relay in D pillar or either rear light cluster.

No fuses under passenger seat to check.

I have replaced both fuses near the battery under the bonnet.

Any advice gratefully received. I’m struggling to trace the wires as they go up the left side wheel arch.

 

[manfrotto]

As Bear78 suggests, I would pull apart the towbar plug and clean up the contacts etc.

 

[StevenH]

As Bear78 suggests, I would pull apart the towbar plug and clean up the contacts etc.

Thanks I did this to no avail.

Also tested my van on another trailer and another car on my caravan and the problem persists.

Next step is to find the bypass relay and check the wiring there.

 

[roadtripper]

From your description it sounds like the right hand indicator has been connected to pin 6 instead of pin 4, and the right hand indicator is not connected at all.



Has this ever worked properly - it's not clear if it has and has failed or if this is the first time you've used it since it was fitted?

Ah you mentioned the audio confirmation has worked before. Does sound like a short in the wiring somewhere, have you had any other electrical work done recently ?