Re: Dimmer wire in MK4 (daves_1.8t)
Hi daves. I'm by no means an authority, but I have a bit of electrical knowledge under my belt, and just swapped my factory Monsoon with an OEM Navi unit a few days ago, so stuff is still fresh in my mind.
First, GoMobileR32's DIY thread for the AVIC-D3 is a good source for finding wires.
http://forums.vwvortex.com/zerothread?id=3134807
Switched 12v is pin #1 at the headlight switch, dimmer control is #17 (grey/blue). GoMobile makes the good point that if your head unit is expecting just a non-variable signal to tell when the lights are on, you should use the grey/purple line (he doesn't give a pin number) instead. I've read some threads about people's head unit freaking out if it gets a low (dimmed) illumination signal.
Also in GoMobile's install, he shows the wire to tap for the S-contact instead of just straight 12v switched. The S-contact goes hot when you turn the key, but stays hot until you take the key out, where the 12v switched will go cold when you turn off the ignition. If you tap the S-contact line instead of switched 12v, your head until should stay on after you turn off the engine, remaining on until you pull out the key, just like the factory radio. It _should_... I make no guarantees.
You can tap the S-contact line at the steering column like he illustrates, or someone else in this subforum pointed out that line is also available at the fuse block.
http://forums.vwvortex.com/zer...75714
I elected to tap from the fuse block to make it look a little cleaner. It's the brown/red wire going in, and I believe yellow/red coming out. Tap the one coming out, so you get the fuse in the line for protection, just in case. Going to the fuse box is a little more work, but not impossible.
I hope some of this helps you get started. And good luck with the install if you decide to go ahead with it!