Fixing sticky/seized door lock actuators
Hi there, I have recently had the same problem on my 300C - basically the door lock actuators started "sticking" and eventually would not pop up enough to unlock the door. The whole lock mechanism - on all doors - slowly got worse over timeand I finally decided to tackle the problem. Attempts to lubricate the mechanism (both externally and internally) failed. I have fixed them all quite easily and will describe the process here:
PROBLEM: the culprit is a plastic lever on the mechanism which rotates on a pressed in stud. Dirt and corrosion from the metal washers has collected between the part and the bearing surfaces causing the lever to seize to a point that exceeds the solenoid's ability to move it. I have attached a pic that shows the location of the problem.
I will paraphrase the FSM procedure for removal (for the rear door - front door is similar - once you have done the rear the front will be more or less obvious):
1. Take off the trim panel (a combination of screws and those little trim fasteners that you pop the center pin through to remove - have some replacements handy - I had about a 60% survival rate for these plastic parts)
2. Pull back the watershield enough to access most of the door
3. You have to take off the rear glass channel - it may not be obvious at this point, but this frees up room to access the lock and allows the mechanism to be removed.
4. Reach in and unsnap the plastic clips that attach the door latch lock link (on the actuator) to the lock button and pull it off the lever, then remove the link and the lock button from the door.
6. Reach in and unsnap the plastic clip for the interior door handle link and pull it off the actuator
7. Reach in and unsnap the plastic clip for the link to the exterior handle and pull the link of the actuator
8. Unscrew the bolts that attach the actuator to the door (three bolts, accessed on the outer side of the door)
9. now the actuator is "floating" and can be moved around inside the door. Remove the electrical connector and then you can remove the mechanism from the door.
Now that you have the mechanism out, you can drill out the post that acts as the bearing for the plastic lever. Once that is done, replace the post with an appropriate sized machine screw with a locking nut. (I used a stainless steel machine screw about 3/4" long, with a Posi-Lok nut. I also had to grind off a bit of the head of the screw so that it did not interfere with the rest of the mechanism) (I also drilled out the plastic lever very slightly to fit the bolt)
BTW, I used bolts and nuts that I had in my "bin of screws" - it is likely that with some effort one could find a more suitable replacement.
I only tightened the nut so that there was little play in the lever and it rotated freely. I cleaned the whole mechanism, lubricated the heck out of everything, and re installed. the installation procedure is exactly the reverse of the removal.
I repeated for the remaining three doors, and the locks have been working perfectly (actually easier to move manually than they ever were which my kids appreciated)
I hope this helps someone with the same problem. The whole job took about three hours and I figure I saved myself about $400 vs simply replacing with new actuators.