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My 3rd brake lights not working on my 2017 polo. Took the led unit out and this works with a 9v battery connected so this is OK. Checked the voltage on the connector and nothing so I expect a broken wire as I don’t believe there is a fuse.

Does anyone know where the other end of the wire goes to so I can check if it has a voltage at the other end? Or any other tips.

Thanks
Phil

Apologies for an obvious question but were you pressing the brake pedal when you checked the supply wire for voltage?

I'd think that this could just be a broken wire in the section of cables and washer hose that transitions from the hatch to the body - ie repeated flexing of this cable when the hatch is opened, has caused a cable to shear.

That can only be proved/disproved by removing the covers/headlining - I think, I've not had to deal with that yet! As that 3rd brake light does not draw much current, then its supply or earth wire will be small gauge so that will make it more prone to breaking I'd think.

Edit:- I'm not sure if it is commoned to the other brake lights, logic would suggest why not, but reality is sometimes different.

Yes, I suspect a broken wire as I have no voltage on this when the brake pedal is depressed. I need to try to find this inside the car and check if I have voltage before the flexible hose in the tailgate. I expect the tailgate has been opened less than 1000 times so surprised it’s failed.

Fun weekend ripping out internal panels

I'd think, the first thing to do will be to investigate the short length of cabling that is inside the rubber gaitor - I don't know how much/far you can compress that gaitor to expose the individual cables for signs of damage, but that would be my first move. If you find a damaged point in a cable, then will be the time to remove trims and feed the damaged area back into the car as a single cable, and solder in a section of same gauge or greater wire, then feed the flying end of that back into the gaitor section and further into the hatch, then pull back the remaining broken end into the hatch and join to the free end of that new wire. One issue you might come up against is that the cableform is wrapped and initially some of that wrapping will need removing and replacing using suitable fabric wrapping tape. Good Luck!

We had this with our 2015 Mk5 Polo and found these forums useful , and I thought it would be useful to report back and I guess is the sane for many VW's
1) There is no fuse for the third light
2) The light was removed by using 2 decent plastic picnic knifes , working from both ends prizing from the top. FYI the little white plastic on the right hand side is the rear washer ,
3) The light was tested, I'm my case by trying in my Tiguan as I had no electrical meter and was fine
4) We slipped off the rubber wiring boot on that connected to the hatch from car ( also has the water for rear windscreen( and cut back on the protective cloth around wires and found 1 broken wire and 1 slightly damaged wire

The wire was re crimped and repaired and all in fine

Hope this help

Good stuff!

Also good to reply to a thread with your experience - some people prefer to post for help - then vanish!

Thank you!