DjaKRAbb

car: c200k w203
Hello, terrible weather today so i thought i'd share how i fixed my door lock actuator problem, because i didn't find anyone with the exact issue.

Symptoms (rear right side door actuator)

• Lock would only work in 1 direction - e.g. mine would only close
• It would close very slowly, sometimes only half way so i'd have to press lock multiple times
• When i pressed open - i couldn't even hear the motor trying to do anything.. silent / no movement on the locking stick.

Diagnose

• Removed the door panel (plenty of tutorials online on how to)
• The door actuator is simple - pos. / neg. wire going to it that come from an ecu type control box.
• I cut the 2 pos/neg wires going to the actuator , stripped them, and crimped on some spade connectors for testing
• I then connected them directly to my own 12v battery
• The lock opened quick... i swapped polarity and it closed quick.. so the actuator is working perfectly. (which turned out to be wrong in the end)
• The next thing in the 'chain' would be the ecu box (shown below)
  
• i removed it from the door panel by pinching the top and bottom plastic pins so i could remove the connector (ofcourse, i learned you need to do this after braking the connector out , the release clip is on the door panel side hidden lol)
• I then turned the connector upside down and carefully reconnected it (reversed the polarity)
• The lock would now only work in the other direction, confirming to me that at least i know this ecu is broken. time to order a used/working replacement.
• The new ecu came, connected it up, and the door lock was now working in both directions! but after a few times locking/unlocking it began to move very slowly again (but atleast this time in both directions)
• At this point - i was not trusting the actuator anymore. but i seen a youtube video (ill credit later) of someone using an external 'universal door lock actuator' to fix this problem.
• So i bought it (4 x cheaper than a used actuator) and installed: (i used a ratchet with phillips to tighten the screws inside the door frame)
  
• i extended the wires of the universal actuator to the wires coming from the ecu (the original actuator has no power going to it anymore)
• Believe it or not, it works perfectly now. you would never know it has been messed with

The youtuber used this method to fix his bouncing door lock also. Try it (i know you already have electrical tape wrapped around atleast one of your locks!)

youtuber name
*What i think happened:
A faulty door actuator pulling too much current each time it was used, leading to the ecu box being damaged.
New control box would be fried by the actuator eventually
So both the control box + actuator where at fault

Thanks for reading