So, your (ancient) C5's headlights won't go up, or down, or sound veerrry bad? You might have a broken plastic (they call it nylon) gear inside the motor gearcase. Here's how you fix it.
   editor says: to keep pics large, you can find them on separate pages from the links below this article. They don't have individual labels - I have not figured out how with my otherwise versatile photo page software.

First make sure the gear is the problem. Check all the wiring for bad spots and good connections. If they both behave the same, check the motor control module mounted below the right side headlight. The problem may also be that the linkage slips past the stops. Simply repositioning the motor towards the middle of the car by placing washers between the motor case and the car may solve your problem. A broken gear may make the headlight feel "notchy" when cranking it by hand. If the linkage travels too far and passes the torn-up travel stop, just turn the stop around and relocate the motor towards the middle of the car by installing washers between the motor and the mounting point.

But if the gear is really torn up, then order the bronze replacement gear, one per side. Find them on-line at Ecklers (dot com) . If your car is 1997 to 1999, you should receive a gear, the rubber insert, and a circular motor gearbox gasket, for each motor. For 2000 or later, the package will contain some epoxy and tools.  More on that below.

OK, find a well lighted, comfortable place to work. Open hood, crank up headlight using the knob on the end of the motor. Remove black bezel around headlight - three screws. Tip it outward from the top front, remove, put the screws in a safe place.

Remove the body panel from the top of the headlight, about four screws, one each side, two on the back. The frame on top of the headlight assembly positions the body panel in the center of the headlight opening. Outlining its position on the top of the headlight assembly with a pencil will save you considerable readjusting for reassembly.

The two bolts upon which the headlight pivots have a plastic bushing in the bolt holes. Don't lose it - it will last a long time, but the bolts and headlight assembly will not operate for long if you lose it. You'll have to grip the bolt head with vise-grips. You can twist the #15 Torx bit right off trying to do it correctly. The self locking nuts probably won't anymore; one of mine fell off once; the headlight gets wobbly in the open position. Unplug the headlight bulbs. If they're original, this would be a good time to replace them with Slyvania Silverstar or something brighter.

Swing the headlight down and out of the way, into the fender. Now undo the headlight to motor electrical connector located just to the rear of the motor. The connector mounts to the car by sliding (fore or aft - I don't remember ) into a small fitting that's permanently fastened in the metal below it. Don't break the fastener trying to pull it off.. Remove the nut that holds the linkage to the motorgearbox. Remember general orientation of parts and the gearshaft, then unbolt motor and take it to the bench.

Back in the car, find all four of the white plastic motion stops, pull them gently off, turn them upside down, and push back into place. You can see one or more in the photos. If one is torn up beyond use, you can get them from the dealer. But they're not called "stops", so you'll have to show the parts guy a picture or find it in the parts diagram in his viewer.

Take motor to bench, remove screws from motor gear case. If you have a 2000 or later, you have a plastic housing which must be pried or Dremeled apart, but the inside should be similar. Note the order of pieces when you remove the innards, set them out in order. Clean out the old grease and busted gear teeth. The gear itself may be broken. See pics. In one pic, the white things like grains of rice are broken gear teeth. In the pic of the motor reinstalled, you can see one of the three washers installed as spacers to move the motor slightly to the center to change wear pattern on the travel stops.

Prep the new gear by trimming the outer "corners" of the slot in the rubber insert. The insert must fit into the recesses in the new gear, like the old one, or in the photo. It won't until you round off the corners to fit inside the rounded recesses in the gear.

Assemble the new parts with the old parts in the same order and position. I greased the gear all the way around, and liberally greased the worm gear in the inside edge of the gearbox (rotate it some) and greased the bushings and case seal bushings. I used lithium wheel bearing grease. (It doesn't take much - I have 3.999 pounds out of 4 remaining if you need it.)

DO NOT USE SILICON GREASE ON BRONZE GEARS !!! Bell Helicopter learned the bronze parts in helicopter fuel controls will corrode in silicon. Dissolve, even.

Ok, those that own 2000 or later - if you bought the correct gear and are ready to reassemble, the glue that came with the gear will NOT work. Cut slots in the case with Dremel and hold the case together with two pair of zip-ties as shown in this photo. Zip-ties that say UV resistant - usually not the white types - will last longer. Seal the cover with Permatex black or similar.  Here's a link to pics and forum article on how to do that case reassembly. Click here and scroll down.

Reassemble in reverse order from above. Adjust the position of the motor by placing 1, 2, or 3 washers on each bolt that holds the motor to the car to move the motor inboard a bit so the linkage strikes the center of the white nylon stop.