Grounds
One of the most useful things to know when diagnosing electrical problems is where the ground contacts are and specifically what's connected to them. For example, if all devices connected to ground G are misbehaving, it's likely you've got a problem (corrosion, loose wires, etc.) at G. On the other hand, if only one of the several devices connected to ground G is malfunctioning, then ground G isn't apt to be the problem.

The color code is simple: All wires leading to a body-ground are solid brown. (Engine-grounds may have other colors.)

Abbreviations
14401: The main wiring harness
A/C: Air conditioning
ABS: Antilock brake system
A-pillar: The roof support at the windshield
ATC: Automatic temperature control (cabin heating/cooling system)
EATC: Electronic ATC
EEC: Electronic engine control
G: Ground connection, as "G1003"
illum: Illumination
LH: Left-hand as viewed by the driver
PRNDL: The shift gear indicator in the center console
RH: Right-hand as viewed by the driver
S: Wire splice, as "S211". Splices are inside the harness and hard to see.
sw: Switch
TFI: Thick-Film Ignition module
T/O: Tape out - the point at which a harness branches to feed a component

Foglamps
The foglamps are among the Scorpio's most infuriating engineering mistakes.

Recently I spent an entire day replacing a bulb and devising a substitute for the broken plastic posts. Perhaps my experience and my solutions will be helpful to you....

Removing the two mounting bolts
Begin with this premiss: the bolts are corroded, and you'll ruin the heads before you succeed in removing the lens. Still, there are two precautions that can improve your odds.
1. From under the car, squirt a generous amount of penetrating oil on the protruding stubs of the mounting bolts. If you have a preferred freeing agent, use that instead; but never try to back out the bolts without something on them to combat the rust.
2. Use a toothpick or some other small probe to remove debris from the recessed head of the bolts. Otherwise, the tool won't seat firmly.

The bolt heads accept two kinds of tools: a T-20 Torxdriver or a 7/32" flat-bladed screwdriver. Please note that these sizes are not arbitrary: using a narrower or wider screwdriver will destroy the head before you can extract the bolt.

In a perfect world the Torxdriver would be the tool of choice. In the real world the screwdriver works better, but you must maintain perfect alignment with the axis of the bolt to avoid camming the blade out of the slot. There will be two difficult moments: getting the bolt to turn at all; and then after a deceptively easy interval that fools you into thinking you've won, getting the trailing end of the threaded shaft to pass through the tapped backing plate. Sometimes you can screw the bolt back in, apply another dose of freeing agent, and urge the bolt all the way out on a second try.

A more desperate ploy, after you've destroyed the bolt head's slot, is to use a Dremel cutting wheel to deepen and widen the slot to accept a larger screwdriver. Be advised that you have exactly one shot at this technique, because there won't be enough head left for a second try.

If all else fails, you can use a carbide bit (normal carbon steel bits are too soft) to drill away the bolt's mangled head altogether. Then after removing the lens/reflector assembly, you ought to be able to extract the bolt's shaft with Vise-Grip pliers.

In my case the corrosion was so severe that one bolt failed in torsion after only about half a turn. I feared I was defeated; but I found that 1/4" of the threaded stub still protruded from the backing plate. With a pair of Vise-Grips while lying under the car I extracted the stub by backing the failed end out through the threaded plate.

Finally I held the lens-and-reflector assembly in my hand, but I was looking at two mangled bolts and facing little prospect of replacing them from local stock. I solved that problem by buying two 2" 8/32 (size 8, 32 threads per inch) stainless steel Phillips-head bolts at a hardware store. These are the wrong thread to mate with the threaded backing plates, but the deft use of an 8/32 tap overcame that. The next bulb replacement will be a breeze, as there'll be no corrosion.

Replacing the broken plastic mounting posts
Some time ago a raccoon, responding to a dare from his sporting friends, challenged my front bumper and hit a foglamp with enough force to break it free from two of its four plastic mounting posts.

(If you've never investigated how the lamps are affixed to the bumper, go crawl under the car now. I'll wait....) Back so soon? OK then, you noticed that the rectangular foglamp assembly has a hole at each of its four corners and that each hole slips over a respective post molded into the inner surface of the plastic bumper cover. In the manufacturing process the posts are heat-deformed like rivets to hold the assembly in place.

Apparently all raccoons know this instictively and in a final act of defiance will try to snap the deformed heads off the posts, freeing the foglamp to flop uselessly inside the bumper. My raccoon gave it his best and left me thinking about how to repair the unrepairable.

The saving grace is that the posts are hollow. This means that after you restore the foglamp to its position on the four posts, you can hold it perfectly in place by using short (half-inch or so) fat sheet metal screws that will form their own thread inside the posts. A washer will ensure that the head doesn't slip through the foglamp's hole.

You'll have to experiment to find the proper screws. When in doubt, use a shorter one. Always monitor the outer surface of the bumper cover as you install the screw to ensure you're not about to pierce the cover from inside. I suggest hex-head screws because in the confined spaces under the bumper a socket wrench is easier to swing than a screwdriver. By using double-sided sticky tape you can keep the screw's head firmly in the socket while guiding the point into the hollow post.

As I said, my raccoon was an amateur and only broke two of the four posts' heads. I decided to complete the job in his honor. I used a light touch with a 3/8" bit to drill away the remaining two heads to allow me to use sheet metal screws at all four corners of the foglamp. This has made the lamp assembly wholly removable for future work on my bench instead of under the car.

By the way, the wires to the foglamp pass through a two-terminal connector that lets you detach the assembly from the main harness. There's only one way to get at the connector: remove the amber turn-signal unit (by freeing its coil spring inside the engine compartment and withdrawing the unit straight out to the side) and reach into the revealed cavity for easy access to the foglamp's connector.

You know, maybe I'm too hard on Ford AG. Who else could take a simple foglamp bulb replacement and turn it into a daylong adventure?

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