This weekend past I needed to remove the front passenger seat in my 124.193. I found the seat controls partially worked; I could move the seat back and down and tilt the back, but could not get it to move up and forward. No amount of working the switches would help. In the past, this has usually done the trick.
I removed the seat control switch from the door, and tested the resistance between the ground pin and the various outputs of the switch, and found increased resistance (~150k Ohms) in one position, so I decided to take apart the switch to see if it could be rescued, similar to the window switches.
The mission: Clean up the contacts inside! Put it all back together and restore operation.
The switch comes apart by removing the screw on the back, and then carefully prying open the plastic around the edges to free the clips, using a flat bladed screwdriver. Go slow, be gentle, as there are many little parts inside ready to escape and hide forever...
Inside you will find about 17 ball bearings, 9 springs, and 8 copper contact rockers. Note the orientation of the plastic sliders that move the ball bearings and the rockers, you'll need to get them back into their original positions.
I decided to only work on only one plastic slider at a time in order to keep them straight. Working from left to right, only the first and third in the bottom row will easily come out. The middle slider resisted removal by gentle tugging, so I left it in place and was able to remove just the copper rockers.
The goal, the copper contacts, are on the underside of the copper rockers and on the surface underneath them. I did not get a good picture of those, but you'll know them when you see them. They are short cylinders of copper, probably black with corrosion. I have circled one in yellow in the picture.
I used a combination of Caig DeoxIT cleaner on a cotton swab and a pencil eraser to get all the contacts nice and shiny. The last step was a wipe with fresh DeoxIT.
CAIG Laboratories - Home of DeoxIT® and Hand-E-Glove®
The head rest up/down rocker is different: no rocker, just a ball bearing under a spring that moves to make contact. I simply cleaned up the three copper surfaces and that ball.
A small amount (as in a tiny dab) of grease on the ball bearings would not hurt anything.
Re-assembly: get all the sliders and balls and springs back in their places, and then carefully put the cover back in place. Reinstall the screw on the back, and then test the feel of the operation of each switch. If anything doesn't move correctly, something moved during the cover installation, so back apart and try again.