Hello, I have a 1990 300CE and I've been troubleshooting the seatbelt butler for weeks now, this is my findings.

When I bought the car both sides didn't work, I bought the whole metal arm for both sides and the passenger side was easy plug and play, and it worked.

But the driver side doesn't work at all, and I've tested every single part and switch working along the arm on the passenger side and they all seem to be working.

I switched the modules around and both of them only work on the passenger, same with the arm itself, also the door switches, and recently I connected the passenger seatbelt buckle to the driver side and still no work.

I tested the pins voltage on both sides and compared them, on the passenger side I have 2 pins giving 12 volts, on the driver only 1 pin is giving me 12 volts.

Also when I close the driver door while the engine is running, the seatbelt butler module starts making a buzzing noise. See video for reference.

https://youtube.com/shorts/JmSiR0GBALA?si=dVYTAWbsG_RM2KTk

Yesterday I jumped a cable from the passenger side pin number 6 I believe, the one giving 12 volts, and connected it to the driver side pin that's supposed to be giving 12 volts, and I managed to get the arm to extend for the first time ever upon closing the door, but it doesn't retract or do anything else, just extends when door is closed. see video for reference.

https://youtube.com/shorts/U4kUHbkPlPQ?si=7ZqNhtBoAqhnKH9e

Now obviously jumping cables from the passenger side to the driver side isn't a solution, as I still have the problem, but I'm reaching a dead end with my testings and getting no solutions, I'd appreciate any help or input.

Thank you.