Sorry to resurrect this, but better than posting a new thread I guess.
So my w169 (2011) handrake does work but there is a lot of slack in the cable. You need about 8 clicks then it’s either on or off. Probably needs a new cable tbh to guve more graduation in the action.
Is there a cable adjustment on the left hand side ? btw I can access the handbrake shoe adjustment , if necessary by removing the rear discs for a final adjustment but that may have to wait till it’s Warmer....now wished I tackled it when I replaced the pads and discs earlier in the summer, but had enough issues with the disc retaining screw....