Third high mount brake light wiring location

[VWTig09]

Hi all,

Hopefully someone can give me a hand with my question.

I want to tap into the power wire for the third brake light above the rear window on my 2009 Tiguan. What colour wire should I be looking for and where would be the best location to tap the wire?

Thanks

[Umai Naa!!]

I think they're all on LINbus in the tailgate, so will all be white.

You'll need to have a look behind the trims on the left rear pillar, where the tailgate harness plugs into the main harness.

Also bear in mind, that tapping into lighting will probably bring up errors on the dash.

[VWTig09]

Some time ago I did remove the left rear pillar just next to the tailgate but did not see any white wires or plugs. Closer to the rear left seatbelt just near the 12 volt outlet I saw a loom with many colours but wasn’t sure where that all went.

So there should be a plug somewhere from the tailgate under the left rear pillar? Ill check it out.

I removed the top trim to access the all-white loom in order to tap the licence plate wires and by chance I found the correct wire that did the job. I would rather be sure though as I don’t want to probe each wire thus pricing its insulation in order to find the third brake light feed.

That tap did not throw any codes on the system as I am connecting in a third party ecu box for towing which is essentially a relay box, so no significant current draw through the car wiring.

Great design hey? Make all the wires white.

[VWTig09]

With that said, what would be the best way in identifying the actual third brake light wire? Even if I do find the loom plug it will have a number of wires I'm sure.

Tracing it from the back of the third brake light seems virtually impossible as everything is tightly bundled and does not move when tugged etc.

[Umai Naa!!]

Can you splice into it at the plug in the pillar?

Then it's just a matter of using a test light to identify it.

[VWTig09]

I’ll go searching for the plug later in the week. Hopefully I can find it.

When I do go though the plug in the pillar I guess I will have to probe each wire there to see which one is +12V when the brakes are on. Just was hoping to not have to probe each wire in the loom and damage insulation. Was hoping someone had already found the wire and could point me to it.

Perhaps that plug can be probed from behind without piercing through the insulation of wires? I noticed the tailgate taillights can be probed through the plug without damage.

[Umai Naa!!]

Yes, back-probe the plug.