First I noticed dimming headlights and dash lights when I applied the brakes while driving at night. My first attempt at a solution was to improve the ground wires from the battery. No change. Next, I noticed dimming headlights after completing a sub/amp install. The amp is smallish, ~300W RMS. The same setup was in my '97 Contour with no problems.
I've only been driving the 2002 Cougar for a few weeks. While rebuilding the car and performing the 3L swap, I noticed the wire gauge used in the Cougar is thinner that what I've seen in Contours. I'm assuming Ford saved a few pennies and made this change. I rebuilt the engine harness in the Cougar using pieces from '97 and '98 Contours along with the '02 harness. I tried to used as much of the Contour wiring as possible, especially for the injectors, as the wire gauge is heavier.
So, now I'm in the process of adding additional 4 gauge wire from the alternator to the battery. Does the "big 3" generally correct the dimming headlights?