Found this doohickey unplugged under the dash of My '87 F250, Is this
that pesky,annoying door chime/key buzzer??

 

Kind of looks like it. What did it do when you plugged it back in?

 

The connector looks about right and if you currently have no door buzzer at all it's a good bet that's the unit. Put the key in, open the door, and then press the connector into that box (but don't fully insert it) and you will quickly find out if you're right.

 

Kinda what I was thinking too. I like the quiet, so gonna leave it unplugged