Dear Friends
It is common to see non working old style power window switches on classic Mercedes. I am referring to the three contact switches which were used from 1965 to 1969. These parts are extremely expensive on eBay and many times you do not have guarantee that they will work perfectly. I took the time to document a recent successful repair that I performed for a W109. I know this is not a MB pagoda specific topic but many of you own W111/112/108/109 which suffer from this problem. These switches work with a negative signal which is commuted from the central post connected to a brown wire to either the top connector (green striped wires) or the bottom post which has black striped wires attached to it.
Here the steps involved on this repair:
1. Remove locking wire style bar at the center bottom rear part of the switches. This bar has faltered ends on both sides, you have to cut with a sharpen wire cuter one end in order to service the internal of the multi switch.
2. Work over a towel or cushioned surface to avoid loosing parts, since internally, this switches have one spring and one metallic ball which will jump everywhere.
3. Remove all the plastic switches and service the internal post terminals which are fused inside the Bakelite switch housing. Immerse this part in an Soft citric acid solution to break the dirt.
4. With a jewelry file, polish each of the post and try to make the surface the flatter you can.
5. If you observe large cavities you will have to fill them up with soldering wire. Use a powerful soldering tool with 80 wats or more. Put some rosin flux paste over each post that needs repairs before trying to fill cavities with soldering wire. Use good quality soldering wire. Warm the surface with your soldering gun and once is smoking bring the soldering wire close to it to melt it perfectly. Do not use much quantity, since you will have to sand it down afterwords.
6. Flatten the surface of each post that has been filled with solder so that it reaches the same level as the wider post next to it. For that, use the jewelry file mentioned before.
7. Lube with silicon paste each spring that has a metallic ball over it. The paste will help to keep ball in place. Make sure that the silicon paste you are using is non conductive (Some have carbon particles inside, this are black in Colour). The test can be done with your multimeter leads.
8. Use gravity in you favor. Put the whole switch housing facing down while you bring each individual plastic switch with the spring and ball facing upward.
9. Have the locking wire bar already pre-inserted on the housing structure so that you can lock the first plastic switch in place...... move the bar enough to keep first switch in place.
10. Have a multimeter on hands and check if the switch is doing its job. Test central connector agains each of the side Terminals by pushing the switch ..... if the switch passes continue with the assembly process.
11. Do the above until you finish assembling the whole thing
12. Once finished put some epoxy glue on the locking bar so that it does not come out by itself.
Enjoy your experiment.
Best regards
L.peterssen
