First things first you need the cover off, some are different then the others, check all around for any time of screw or bolt, or plugs to cover the screw or bolts, if non, then take a screw driver and gently but firmly pry off the cover, once the cover is removed, then it should be pretty straight forward, if you are replacing the seat belt, then you need to replace the entire retractor as well.
Here are some diagrams to help you get the problem fixed. See if the belt is folded inside the retractor.
Please let us know what you find.
Images (Click to enlarge)
Thursday, May 17th, 2012 AT 7:27 AM