I used to have 2 940s (only 1 now) and one of those was a 94 sedan. The seat belt reminder relay is the same as the indicator flasher relay and only works on the driver's seat. To confirm have a look at the middle row of relays behind the fuses, 3rd relay from the left is the flasher/seat belt reminder.
If your seat belt reminder isn't working (but your indicators do) check under the driver's seat for a disconnected electrical plug (4 pin I think). It's possible someone unplugged the seat belt catch because the relay wouldn't stop clicking even with the seat belt done up. That happened to my car. The only way to fix it is to replace the seat belt catch on the side of the seat.
