I just experienced the problem of the key switch going out on the drivers door - in my case it arms the alarm fine but the microswitch seems to be iffy in the disarm direction with about a 50% success rate. When it goes off go around to the passenger door and turn key to shut off.

In looking around most people just disable the alarm rather than pay the exorbitant $140-180 for a wired microswitch

Anyway since I have a parts car I checked both switches from there - the switches are identical and will fit on either side. However Mercedes in their infinite wisdom wired the pins opposite. So since the drivers door generally gets 99% of the use you can swap the switches provided you cut the harness and swap the two appropriate lines.

This also opens up the possibility of getting a passenger assembly from a junkyard and just use that switch (again you will need to modify the harness.

The connector is circular 3 pin with a flat - pins arranged in a triangle two on the flat one centered above (as you look at the pins). The top pin is the common pin the bottom two swap between driver and passenger door.

Figured this may help
Paul

hi

did you take a closer look at the wires in the plug? maybe its possible to remove the wires from the plug without cutting them .

how has your fix worked out for you so far, is the "new" switch working?



its been about 4-5 yrs since i have worked on the alarm microswitches, but if i recall correctly, after separating the door lock cylinders from the

microswitches, when i operated the microswitches by hand, they both worked (engaged/disengaged the alarm) leadin me to believe that the

switches were not at fault , but rather it seemed like the microswitch had made a groove on the outside metal housing of the door lock cylinder , and

that this was causing the intermittent alarm disengagement problem.

Here is a picture top switch is passenger bottom is driver - no real difference. I forget which side the lock is from but no groove just a bit shiny where the switch would run. I have the other side and that one shows the same wear - no groove. In fact the only difference between the two lock assemblies is where the switch cam is, on one side it will engage the switch earlier in one direction. However that should not even matter as you need to do close to a full turn to engage the lock mechanism. So you could probably swap the entire lock assembly again the only change needs to be a rewiring of the switch. In playing around with the old ones now it looks like the driver switch itself could be a bit worn or loose, as it engages better if you hold it down when you turn the key. perhaps a couple wraps of electrical tape would also work.


There is no real way to pull apart the switch housing - it is a Kissling switch, quick google indicates they are Swiss. Also the connector is an overmold so that does not look productive method to get at the wires.

i believe my door locks behaved like yours, it took a deliberate, complete turn of the key to get the alarm to disengage.

am curious , what were you thinking about wrapping in electrical tape?

yeah, its been a long time, looks like i forgot what the microswitches looked like. based on your pic, i guess you are right about the wires not being removable from the plug/connector.

good luck. hope you get them switches working again