Seat Belt Buzzer - April 2016
Inexplicably, as I was just driving along in the middle of South Dakota with my seat belt on and some objects sitting on the passenger seat, the seat belt buzzer went off, and the warning light on the instrument panel lit up.  At
first, I thought that it was probably just due to the fact that I had some weighty objects on the passenger seat, (where the seatbelt was not buckled). 

But after removing the weight from the seat, the buzzer kept sounding.  I found that I could only get the buzzer to go silent by taking my seatbelt OFF while the car was in Drive. I drove the last 1000 miles home without wearing a seatbelt, rather than listen to the noise for the 20 hours.  Thank goodness it didn't fail in such a way that the buzzer sounded while in Drive, regardless of the belt would have been a long drive home listening to that.

I vaguely remember having the same problem with my original '73 LeMans.  The buzzer may have gone bad on it in a 
similar way.  Or it just may have been that it was so annoying to have a seat belt warning buzzer that I got under there and yanked it out.  Seat belt buzzers were a new thing in the 70s.  We regarded them as an intrusive nuisance and car manufacturers hadn't gone to very great lengths to make it hard to turn them off permanently.  In the case of a 1973 LeMans, the offending unit is easy to find.  While the evil thing is making its noise, listen and feel around amongst the wiring around and behind the steering column under the dashboard until you find something that's vibrating.  That turns out to be a small blue plastic three-pronged relay box.  Unplug it and both the warning buzzer and dashboard light stop misbehaving.

I left the seat belt buzzer unit that I removed in the trunk when I left the car with my local GM dealer for the heater core repairs.  They, without my requesting it, plugged it back in under the steering column.  And it has worked properly every since.  I don't know if they had to repair anything - it's not mentioned in the paperwork.  Maybe it just needed to sit in the trunk for a month and self-repair.

$ 13,324.51                    Previous Total            
$          0.00                    Seat belt buzzer repair, GM
 $13,324.51                    TOTAL TO DATE