Try disconnecting the buzzer to see if the light keeps coming on when you hit the brakes.

 

I have the CD-ROM of the Chilton's Manual, has a .pdf of the electrical schematics for the '92 Silverado. I have an older year truck which shouldn't be that different so as soon as I get home, I'll look it up and I could send it to you.

 

With the brake lights, did you recently do any brake work on your truck? You may want to double check the drums, calipers and brake lines to see if there is a leak which may allow air into the lines. About a month ago, the brake cylinder for the drum popped the boot, leaking brake fluid all over the place. After getting that fixed, the brake light stays on.

I tried to bleed it once but there must be a lot of air in the rear brake lines and will have it done at the next service for my truck.

As for the buzzer and seat belt indicator, you may want to double check the wire cluster inside the engine well, up against the front firewall and see if there is any water on there, if there is, then that maybe causing the those issues. To resolve it, get 2-1 dielectric spray and spray it down.

That would be my 2 cents...

 

thanksfor all the help