The Crown Victoria (and subsequently, the Grand Marquis) came equipped with a lighting control module that served a dual purpose, both for
civilian use, and for fleet / police use. You might have found this page because you were wondering about a wire with disconnected blue connectors located under
your dash (as shown above). This connector will allow you to enable or disable the vehicle's "Dark Car" mode. A simple write-up by John Gislason (11/25/2001) will
explain everything you'll want to know about this "dark mode" feature:
The current production Ford products have what is called a “Lighting Control Module”. This “LCM”, as it’s called has TOTAL control over virtually every light installed on the vehicle. It takes inputs from various sources and provides lighting control in accordance with it’s programming. For the owner, there are not too many “features” that we can re-program at the user level. One is the DRL function (if equipped with daytime running lights), and the other is “Dark Car”. The Dark Car (DC) mode is common on Police and other Law Enforcement vehicles. It allows the opening of any door without the chimes or dome lamps being activated. This mode is entered by grounding a specific terminal on the LCM. The CV/GM/TC have this grounding connector supplied by the factory, and left in the open circuit application (normal lighting). The connector is located near the top of the carpeting just to the right side of the center console, and is a single pole blue connector (one wire in, one wire out).
To ACTIVATE Dark Car:
-disconnect the battery, or if you prefer, pull fuses #4,8,&12 in the central junction box.
-locate the blue connector to the right of the central console (near the carpet edge) and plug the two ends together
-reconnect the battery (replace fuses)
-cycle doors to verify changes
Note: the dome light will remain operational from the Headlamp switch position
To DE-Activate Dark Car (enable “normal” dome lighting):
-disconnect battery (or pull fuses)
-locate and disconnect the single pole blue connector to the right of the central console
-reconnect battery (replace fuses)
-cycle the doors to verify changes.
The LCM needs to have it’s “keep alive” power interrupted to cause it to re-examine it’s programming, so you do need to disconnect the power sources before any changes will take effect. I suppose, you could just unplug the harnesses to the LCM to disrupt it’s power, but I’d much rather pull fuses than “stand” on my head pulling connectors.