Hi all, 2012 Octavia 2l tdi

Brake lights are not working.

I had hitched up a trailer (that had not been used for some time) checking the the lights and found that the brake lights did not work either on the trailer or the car (car ok up until then).

Disconnected the trailer, car brake lights still not working.

I assume that there was a problem with the trailer brake lights and that maybe blew a fuse in the car.

But I can't identify a fuse for the brake lights can anyone help please, which fuse should I be looking for? Is if in the interior fuse box or the one in the engine compartment.

Thanks.

I

Since my previous post I've learned that the fuse may be no. 13 but that appears to be intact, maybe that's not the problem.

The brake lights and the side lights are the same bulb on later models. The intensity is changed electronically using pulse width modulation.

I suggest you check for fault codes.

It may also be that the car has shut off the car brake lights for protection against a fault in the unit that creates the brake light supply to your trailer brake lights.

Take look in the boot on the left-hand side for water ingress and corrosion of the connections made to the earth stud. Also look at the wiring to the trailer socket for shorts.

34 minutes ago, pikpilot said:

The brake lights and the side lights are the same bulb on later models. The intensity is changed electronically using pulse width modulation.

Since posting I checked again. Only the estate is as described. The hatch back/saloon still has a two filament bulb with separate feeds for side and brake lights.

Check your handbook for fuse function. Mine says fuse 13 is the diagnostic socket.

6 hours ago, pikpilot said:

Since posting I checked again. Only the estate is as described. The hatch back/saloon still has a two filament bulb with separate feeds for side and brake lights.

Check your handbook for fuse function. Mine says fuse 13 is the diagnostic socket.

Thank you, I had already checked the handbook which does show fuse 13 as the diagnostic socket + light switch, but some online resources also show brake lights and I can't see any other reference to a fuse for brake lights.

I'm beginning to wonder if, unknown to me, there was actually a problem with the brake lights on the car before I plugged in the trailer!

As far as I can tell, there is no brake light fuse on your model, suggesting the lights are electronically controlled too on the hatch.

When you have tried everything else and not found anything, I would do the car version of Ctrl+Alt+Delete which is to disconnect the battery for a few minutes as a reset. You will loose your trip data and have to reset the one-press open and closure of the windows as shown in the handbook.

Cabin fuse 2, a 5 Amp one, I think.

Engine code and build date would help confirm (I can find those via reg or VIN).

Edited 22 July, 202522 Jul by Breezy_Pete

Thanks for all the replies. The problem seems to have gone away, I had pulled various fuses trying to find one which had failed but none had. However pulling fuses caused some functions to reset, trip meter, clock etc, perhaps that in some way caused the brake lights to work again.