FYI wiring for automatic headlights

Here's the easiest place to access wires for adding automatic headlights. I'll be using the DEI 545T automatic headlight module, but you use whatever you want. I've searched the forums and others have posted where they tapped into wires and how they wired up the lights, but some are needlessly difficult and others are just wrong.

Location of connectors: Pull open the panel to the lower left of the steering wheel. There's no need to disconnect anything, just let it hang.




Connectors: You will be splicing into wires from these 2 connectors. These connectors are for the BCM (body control module)




Headlight control wire: The wire you need is in the smaller white connector. You will splice into the blue wire, above the yellow wire towards the lower right of the connector. GROUNDING this wire turns on the headlights AND parking lights at the same time. (If for some reason you only want to turn on parking lights, you can splice into the yellow wire.) Again, this is a GROUND (NEGATIVE) controlled wire. DO NOT provide +12V to this wire.




Ignition power wire: If you need +12V to power a device such as the DEI 545T, a relay or whatever you will be using, you will splice into the blue wire at the lower right corner of the larger connector that has the black lever. This wire is powered when the ignition is on. It comes from a 10A fuse that provides power to the instrument cluster. A DEI 545T or relay pulls such little current that it will have no effect on this circuit.




Tips on splicing: If you use a "T-Tap", it will likely fail over time. I've wasted many days of my life tracing faults due to these stupid T-Taps. The best way to tap into a wire without cutting the wire is to strip off a small section of insulation and solder on your tap wire. Then, tape the splice and secure a cable tie / zip tie over the taped splice, as pictured here.

 

Sorry, not sure what you mean by "headlight parking lights". The blue wire in picture#3 turns on headlights AND parking lights at the same time. If you just want to turn on parking lights only, that would be the yellow wire just below that blue wire.