Sea belt buckle
 

seat belt buckle
 

The costs depend on whether your buckle system has a pretensioner or not. If you have a buckle pretensioner the complete replacement will probably cost you up to 1000 USD (worst case). Half price without.

As a former buckle/buckle system developer I would suggest to proof the functionality of the buckle first. Does any part of the buckle move? Maybe parts of the buckle adhere to clammy contaminants. If parts are cleaving try to funnel clear water into the buckle (through the slot of the tongue) until it is working again (catch water at the end of the buckle with a bucket).

If this isn`t leading to success try to look inside the buckle. Maybe a steel feather (ejector spring) was falling out of her bearing. Try to mount her back to her position (very difficult if you don`t know the system). Maybe you bring home the bacon...

Otherwise:
If the above written method doesn`t also lead to success, open the buckle covers with a srew driver (maybe the covers are joined with 2 srews or by clips). Normalwise you have to take a torque screw driver if there are screws. If there are clips (snap-fits) you have to open the caps with force (the joining of the caps will be destroyed). There is no other way to remove parts (you cannot remove the buckle). After removing the covers open the buckle and have a look what part is failing. Regularly you will find a dislocation of parts (mostly feathers). Otherwise there will be contaminants in the buckle - remove them if you see any. (If parts are broken you have to replace the buckle professionally.) You can try to latch and delatch the buckle without any latch. Latch the buckle while compressing the ejector and delatch by pressing the pressbutton.

After repairing the system trim the covers with a gripper and stick the trimmed covers together with superglue (put the superglue only on the connection edges).

This is the cheapest method to repair it....

Kind regards
Oriette (Switzerland)