[Mike Garrard]

Not Volvo's best engineering but nice looking. Hence the need for spares. The turned rod in the bottom middle is a two tooth tool that can be held in a vice to undo the stem nut, which then releases a tensioner spring and a steel cable that rusts, with cap. I've repaired in the past using 4 brazed bicycle cables, just visble inside the pot. I think probably a length of M4/M5 studding would be less 'springy' but much easier.
Spares for experimentation: £15 inc. shipping.