Brittle rubber seals that let in water and drafts, worn window cords and tired springs are the most common reasons the front doors on a 122 with a B18 or B20 engine need attention. Once a seal has dried out and cracked, moisture starts working its way into the door, which over time feeds rust in the lower door panel – so it's smart to replace the seal at the same time as the window mechanism is refurbished.
This group includes fasteners such as screws, washers, lock washers and nuts, together with rubber seal, window cord, spring and side window. When going through the front door, the glass edge, the cord mounting and the spring tension are typical check points – a worn cord gives a sluggish or jumping window, while the correct lock washer keeps the mounting in place despite vibrations from the road.