Not a big job, when window open, few screws along edge, drop mechanism out, probably find frame holding the gear in the middle has split. fit new one screw up job done. If window not open, fiddly, I have used a screw driver, to turn the gear, pressing to the opening edge, to engage gear, might be stiff if not opened for some time, failing that, if on night latch, thin piece of flat metal strip, slid in to the opening, to where the locks are, push them open with metal strip
SD, September 2011
