560SL height adjustment
I'm pretty sure that the small spring for the pawl on the ratchet mechanism has come off, maybe broke. it's a 20 cent item, may want to order the MB one to get it right the first time. You can compare the drivers to the passengers side to see which spring it is. Maybe it's even still there, laying under the seat or hanging on to one side. Just fixed 2 of these this summer. It's do-able without replacing the seat, but be patient and persistant. There's a few different springs under there, this one is small, between and inch and two inces long when tension is released, really light, doesn't do all that much, just holds the pawl engaged to the gear when adjusting.