newbie, how do i know which wire is which

Printed From: the12volt.com
Forum Name: Car Security and Convenience
Forum Discription: Car Alarms, Keyless Entries, Remote Starters, Immobilizer Bypasses, Sensors, Door Locks, Window Modules, Heated Mirrors, Heated Seats, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=134008
Printed Date: July 07, 2025 at 10:39 PM

Topic: newbie, how do i know which wire is which

Posted By: nigel_miguel
Subject: newbie, how do i know which wire is which
Date Posted: April 08, 2013 at 12:04 PM

i have a homelink module from a 2011 Audi A4, it has three wires
one brown
one WHITE/ black
one purple / YELLOW

one must be ground
one must power (+)
the other illumination.
How do i figure out which one is which? Can i do it with a multimeter?

thanks
I'm really new at this.

thanks again

Replies:

Posted By: nigel_miguel
Date Posted: April 08, 2013 at 1:11 PM

is there no way to test the unit without being plugged in? I need to find out which wire is which so i can hook it up properly.

thanks

Posted By: offroadzj
Date Posted: April 08, 2013 at 2:24 PM

Typically you will need to find a wiring diagram from the 'donor' vehicle to know for sure what wires are what. Going from my knowledge of typical VW/Audi wiring, I would GUESS the following:
Brown - Ground
WHITE/ black - 12v constant
Purple / YELLOW - Illumination

Note that these are merely a GUESS at the wiring and connecting them like so could damage the module. Your best bet to be sure is to find a wiring diagram via google.

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Kenny
Owner / Technician
KKD Garage LLC
Albany, NY 12205

Posted By: nigel_miguel
Date Posted: April 08, 2013 at 3:02 PM

If i can't get wiring diagram. (i've looked for one).
Is there away to test the wires with a multimeter with a power source? Could i use a 12V battery?

thanks

Posted By: howie ll
Date Posted: April 08, 2013 at 4:21 PM

Brown will definitely be the ground, the other two don't correspond to VAG colour codes, unless by illumination you mean headlights which are WHITE/ black for low beams.
Constant would be red or RED / XXX.
Ignition black or BLACK/ XXX.
Illumination would be grey or grey/XXX.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Posted By: simplyfalling
Date Posted: April 08, 2013 at 4:45 PM

WHITE/ black is 12v, brown is ground and the purple / YELLOW wire is data.

Posted By: nigel_miguel
Date Posted: April 09, 2013 at 1:57 PM

How can i test if the unit actually works? Can i hook up the brown wire (-) to a negative post of a 12V battery and the WHITE/ brown (+) to the positive post on the same battery?

thanks

Posted By: felixdkat
Date Posted: April 13, 2013 at 11:49 PM

a ten dollar electrical tester would be a good investment right about now....

testertester link

this type pierces the wire.

making sure you know what the wire is doing before you connect to it would be a good idea imho.

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