124 Seat Belt Extender

I believe I read somewhere that dirty pin switches may cause erratic seat belt behavior in the 124 Coupes. I searched the archives and could not find a thing.

The extender arm on the passengers side of my coupe has started behaving strangely. Open and Close the door and the arm may or may not extend. If it does extend, it may extend fully and then immediately retract or it may extend partially(any where from a fraction of an inch to a few inches). When it only partially extends, it usually pauses in place for 10-15 seconds and then retracts.

~ Would someone mind giving me a class on the theory of operation for these extenders?

~ Is there a sensor in the seat to tell the arm if someone is in the seat or do they extend anytime the door is closed?

~ Is there a timer keeping the arm extended for a pre-determined period of time?

Thanks in advance for any help...

Chris