How do VW MK6 Headlight Switches Function?

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jtdi33

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Hello All,

I have VLAND headlights from overseas and of course they're wired wrong (lol get what we pay for).

DRLs do not work, even with the supplied adapter harnesses.

I have some knowledge of electronics, and I believe my rewring idea should work.

The one thing I'm not certain about is whether the headlight switch is a "direct connection" to all lights involved, or does CANbus switch the circuit on when the headlight switch is toggled?

I'm trying to figure out the best diode/resistor to splice into a wire in the event that CANbus does control the "switching of the circuits" and thus anything outside normal parameters (current back flow) would cause a CEL.

VLAND has wired the U-shape LED lights to come on with the headlights: I want them to work as DRLs, and in conjunction with the headlights, and high beams if I'm super lucky!

Thoughts?
 
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langers2k

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The light switch only connects to the BCM, there is no direct connection to any lights.

The BCM will then turn on/off any lights required but will also do bulb monitoring etc.

You might want to make a wiring diagram so you know exactly how the different functions are actually wired and therefore which BCM pin they go to. Then you should take a look at the BCM EEPROM and how it can be tweaked, it's not something that VCDS can do but it's the only option on this age of car. It worked well for me to avoid load resistors on a similar Skoda when I switched taillights and added various LEDs.
 
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DV52

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@jtdi33 : Hi. I'm not sure what "my rewring idea" is - but hopefully, my very cut-down diagram might be helpful (note: the arrangement below is taken from a RoW vehicle)

nABFGt0.png


The key to the diagram is the DIN 72552 designations (like "15a"=switched battery volts and "31"=earth) on the Light Switch. I assume that you are familiar with these designations.

So, if I'm reading the set-up correctly - the trigger pin for DRLs is determined by pin#9 on E1 ("TFL"= DRL). Notice that the common end of the 4 x switch mechanism that selects the light function is connected to pin#8- which says "30a" (T30 = hard battery volts). This strongly suggests (to me, at least) that the DRL turn-on signal comes from pin#9 as +12Volt. This means that the status of E1 in my picture is shown with the rotary switch in the "0" position (i.e, DRL turned-on).

Now, as @langers2k has said, pin #9 does not supply the actual DRL, it's just the trigger signal to the BCM (J519 in my diagram). But, if you intend to by-pass the BCM, pin#9 could be useful to also turn-on the additional circuit (perhaps via a relay, or some other form of controller?)

Anyhow - it might be useful to grab a multi-meter and confirm that pin#9 on the LDS has rail voltage only in the DRL ("0") position

Don
 
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jtdi33

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I'll try to get a diagram up, especially when I rewire the lights. This is a low priority project, but everyone's initial answers have confirmed what I thought, a computer circuit tells the lights to turn on.

So, I'll separate the wire for the U-shape DRL shared with the wire for the headlight in the headlight housing, then I'll re-pin the U-shape DRL wire into the pin slot that should be the DRLs on the headlight itself. I'll validate there is no bulb out on the dash, and add a resistor that matches my OEM high beam bulb if there is a code. Thankfully my old headlights are here to reference.

After that, I'll code the DRL to be on with the headlights and high beams. I want to code my fogs to stay on with high beams anyways, I never have understood losing side visibility when the brights are toggled.

What tools do y'all like for releasing VW pins in a harness?
 
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Uwe

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What tools do y'all like for releasing VW pins in a harness?
We had a thread about that a while back:

-Uwe-
 
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