Seat belts are an often overlooked pain in the ass when it comes to the 180sx, if you are looking to replace your front and rear seat belts or simply install some into a car that was once stripped out to be a track car, you need to make sure you are getting the correct belts.
There is a difference between the years for the seat belts and if its out of a s13 or 180sx, the difference through the years relates to the different buckle styles
Example picture
Example picture
The year difference also relates to the rear seats whereby the middle seat in earlier model 180sx/s13 can be different
Example pictures
Example pictures
Regarding the difference between s13 and 180sx seat belts, the fronts are the same however the rears are different due to the mounting style. The s13 rear seat belt bolts to parcel shelf where as the 180sx mounts to the rear pillar (c pillar)
Example pictures
Example pictures
Troubleshooting
As seat belts get older they can experience a number of problems from fraying of the seat belt itself, to slow reaction, to no retraction at all.
For the front seats it is common to develop slow retraction which can have a quick and easy fix, on the actual seat belt retraction device there is a brown plug which connects into the unit.
Example picture
Disconnecting this plug seems to restore the slow retraction for some people. If this fails to help then its best to look to get new seat belts, tampering or attempting to fix the internal retraction mechanism is not advised. Its a safety thing.
It is also suggested that slow retraction for seat belts both front and rear can be fixed by cleaning your seat belts.