83 SC-buzz noise in dash

[DGW]

I've owned this car for 20 years and this is new. I returned home yesterday, turned off the engine and opened the door to get out. A loud buzz noise started behind the dash. It stopped when I closed the door and started again when I opened it. Pressing the door button that controls the inside light stopped it and it did not resume.
It sounds like a noise that might come from a warning buzzer if you leave the lights on and open the door with the key in the ignition, but this has never sounded in 20 years. The noise was definitely from behind the dash gauges.
Anybody have any ideas?

[DGW]

One bump.
Does that oxygen sensor/mileage counter thing (controls the OX light on the dash) have a buzzer?

[billybek]

No, it doesn't have a buzzer, but it may be a relay buzzing...
Did you have the key in with the door open? Does it sound like a buzzer or irregular like a relay that is not quite pulling in?

[schoward]

if key was in ignition, this is correct. The buzzer relay is behind the gas guage. It is the same buzzer that should sound when fasten seat belt light comes on.

If your dome lights work when door is opened, I wonder is relay is old or the wires that connect to it at the bottom may not have good contacts.

You can access the relay from the trunk. Square relay that is mounted to a little plastic platform just behind gas gauge

[DGW]

It was definitely a buzzing sound.
I'll look for the buzzer relay although I always assumed it was long gone. This does sound like the most likely candidate.
I don't remember about the key, I usually take it out before opening the door.

[DGW]

OK, the buzzer relay was still in there. I was surprised as it has not buzzed for 20+ years. I removed it, but can't really verify that as the solution, unless the buzzing starts again. However, everything seems to still work, so removing the buzzer doesn't seem to be detrimental.

Thanks guys!