
In my '90 Honda Civic DX seat belt buzzer goes on for six rings whether seat belt is left in its sliding door hookup point or not.
I have always unhooked it every time I get out, as I don't like designers' assumption that I am too stupid or lazy to hook it up myself. And the
resulting mindless, insulting buzzing.

When I get in and hook it up, even if I get it hooked before the buzzer sounds six times, it doesn't quit its six ring cycle.
The point: the thing has nothing to do with prompting you to hook up.
It just buzzes mindlessly. Also, it doesn't really "force" you to hook up,
because, even if you don't, it stops after six buzzes.

So those who mock others for being "unsafe" by objecting to it have no point. Nothing you do will stop it. It is such a poorly designed system that it has nothing to do with safety. It's just insulting.
The point: it's a very poorly designed, brainless system. It should
Let you know, perhaps, if you forget, but not sound every time, for
one thing.
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TO DISABLE IT: I found that, even if driver's belt is stretched out,
and not hooked, it does not stop. So the nylon ties solution of one
blogger, at least on my '90 Civic, would not work.
You can fool it all you want at the spool, and it still buzzes.
HOWEVER: The "green plug" advice did work. It's behind and to the right of the radio. There's space back there by just reaching from passenger
floor area, without touching the radio. Pull back that corner of the
carpet, and there is a black plastic square cover over it, so pry, or whatever, that off (mine was already loose) and the plug is, indeed big and green.
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Regarding the comments about unplugging it:
I did find that if it is un-plugged the door hookup slider stays at the front, near the dashboard, not slid back to where you hook up to it.
Using a little logic, I saw that what moved it was a motor somewhere
which is activated by the green plug. Thus some have said: if it is
un-plugged the seatbelt system is unusable.

THE SIMPLE SOLUTION TO THAT:
Be in the car with the door closed, so the slider is up where it needs
to be. Then without opening the door, unplug the green plug. Thus
there is no motor to pull it back up to the front when you open the
door and it stays up, just like in a real car.
The one little thing I noticed is that the passenger door had been
open, so only the driver's side unit is parked up. Soon I will plug it back in, make sure they are both up, then unplug it.
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The result is amazing:
NO NOISE, NO MATTER WHAT. AND SEAT BELT IS FULLY FUNCTIONAL.
I do, find, however, that it does make it possible to forget to use the
belt. That's new. But I'm a belt user, so I soon remember and hook up.