Seat belt buzzer and light won't go off

Hey guys,
I have a tiny problem with my seat belt buzzer system thing. It was already faulty when I've bought the car. When I sit in the car and turn the ignition, the buzzer and buzzer light goes on, so far so good. Now, If I put on the seat belt, the buzzer won't go off.
Because I didn't care about the dash light in the first place, I've unplugged the buzzer itself but when I drove the car last weekend, the buzzer light went so hot it started to melt the dial.

How can I find out what is wrong? I am completely brain dead when it comes to electric/electronic stuff...

Oh we're looking at a 1974 built Plymouth Valiant base model (VL41C4F *** ***)


EDIT: I've just found out that the buzzer I was talking about might be the headlight buzzer but what's weird is it won't go off either....?

View attachment 1716233472

View attachment 1716233473
That lamp looks bright and the lens is showing heat damage. Definately on too long. Maybe a short.
I won't have a chance to look at the books until later in the week.

Your Valiant has the heavy duty wiring and back window heater grid. yes?
Maybe @townsend or @Bugman will know or be able to look into it.
Did the car have seatbelt interlock originally?