If you examine the buckle that you snap your seatbelt latch into, you will notice it has wires attached. That is where the sensor is.
Seat belt cilker.
If there is weight on the seat, it senses that (probably a spring systme), and if the seat belt isn't in the buckle (there's a sensor there as well), the light flashes or it beeps.
Because they dont have sensor in seat
Which "sensor" are you asking about? I have many in my truck beginning with the seat-belt sensor that says if I have buckled-up or not.
There is a sensor in the buckle.
On a 1975 Corvette, the seat belt sensor is typically located in the seat belt latch assembly, which is mounted on the floor of the vehicle. This sensor is designed to detect whether the seat belt is buckled and to trigger warning indicators. The system may also be integrated with the ignition to prevent the car from starting if the seat belts are not fastened. For precise location and functionality, consulting the vehicle's service manual is recommended.
It is probably because the sensor under the seat for the seat belt has disconnected --Same thing happened to me. The light would go out when I pulled on the seatbelt. The reason was the simple fact that the belt was twisted before it came out of the shoulder "bracket". Oh... The sensor is in the door post, not under the seat. I also thought of that eventuality and checked. Nope, no sensor under the seat!
Is this a safety issue
unplug the sensor attachment from right under the seat
the receiver for the belt has a sensor. if it fails the light will continue to flash even though the belt is buckled. replace it!
Under the seat there is a wire that runs to the seat belt lock. It has a conector which you can unhook. With this disconnected, the bell will not sound while you are in seat without the seatbelt buckled.
If the warning sensor for the seat belt does not activate when the driver's door is closed, it could indicate a malfunction in the seat belt sensor, door switch, or the vehicle's electrical system. The door switch may not be properly signaling that the door is closed, or the seat belt sensor may be faulty. It's advisable to check the vehicle's manual for troubleshooting steps or consult a professional mechanic to diagnose and resolve the issue.