I just had the alternator replaced today with a new mechanical type voltage regulator. When I turn the ignition key to on, the regulator is buzzing; the buzz goes away after I start the engine.

What kind of problem am I looking at ?

mechanical type voltage regulator???????

I'm referring to the original type larger than the electronic ones and kinda square...

Huh?
There was only one!

Mechanical? What's that? It's an electronic voltage regulator. Simple part. Nearly never fails.

Huh?

The generator and regulator are working fine. The problem is the regulator buzzes when I turn ignition key on. Buzz stops after engine starts

where does the noise come from?

From inside the VR, goes away after engine starts

Early regulators were very simple. They had a voltage sensing element and a relay. When the voltage dropped below a certain value, the relay would close to energize the armature and turn on the generator/alternator. When the voltage reached a higher preset voltage, the relay would open and turn off the generator/alternator.

Do the above real fast and you have a buzzing noise. You should be ok unless one of the following is happening: 1) the buzzing is getting louder, 2) the voltage regluator isn't working right, 3) the buzzing noise is annoying to you.

Spoke

Thanks. Any idea why it only does this when ignition is only and engine not running ?