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I would also be interested in understanding the wiring a bit more. I'm aware the leads from each fog lamp unit should be connected to Pin 45 (for LHS) and Pin 5 (RHS) of the BCM.
^^^nibose: hi
On MQB platform vehicles like the mk7.5 and the mk7, you need to make a mental separation between the actual light fittings and the LDS: both items are indeed wired to the BCM (as you correctly say) - but it's useful (IMO) to think about the fog-light fittings as being connected as "outputs" from the BCM and to consider the LDS to be an "input" to the hex09 module.
This is a tad different to traditional lighting wiring - but consider the BCM as a kind of "fat controller" (of Thomas-the-tank-engine fame) for the car's 35 x exterior lights.
Here's how the front fogs are wired (it's as you describe in your post):
Shouldn't there be a connection from the LDS to the BCM as well or is it already taken care of, because I've already got rear fogs installed?
What an excellent question!!!
Here's my guess of how the LDS is wired to the BCM (I'm guessing because the official WD doesn't show the LDS internals)
"J519" is the BCM.
Apropos of the answer to your question -the unusual thing about my guesstimate arrangement above (for me at least) for your project is the fact that there is only one wire from the LDS to control both the rear and the front fogs (isn't that interesting?). I've pulled apart a LDS and there's a piece of electronics inside the LDS that sends a different signal depending on the switch position. That's why I have shown a box with a transistor symbol on the LHS of the LDS in my picture.
Here's a set of oscilloscope traces that I took that show the nature of the fog light signal from the LDS (ignore the bald headed Adonis holding a camera in the background):
I suppose that the BCM could simply look for 3 x different voltages (OFF/Front-fog/Rear-fog), but I'm not sure if it's this simple. Perhaps you have your own hypothesis-maybe?
So as a final statement, the answer to your question is (surprisingly) NO there is no additional wire needed from the LDS to the BCM for the front fog facility (because there are extra smarts inside your new LDS).
Don
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