My brothers car died, I had this 2004 s10 blazer sitting in my driveway. I WAS going to sell him it pretty cheap. It’s been sitting for a few months and had collected a bunch leaves where the windshield meets the hood. I pressure washed it and used air compressor and blew all the leaves out. I then went to connect battery. As soon I touch the 2nd terminal it started making this noise. Initially I thought it was something with the starter I replaced recently. It wasn’t it. I located where the noise is coming from. I have a longer video but it won’t let me upload it. So if anyone has ANY suggestions I would greatly appreciate it.

 

It’s on the passenger side, under the airbag area. If anyone has an idea I can send a longer video.. just too big to upload on the forum

 

Bit of a wild guess but I could see how a bad blend-door actuator might be causing this. It is in the right location.

The blend-door actuator controls the air flow in the HVAC system to control the temperature. It consists of an electric motor and a couple gears that can get stripped. I can imagine the electric motor trying to cause the gears to move but if the mechanism is damaged or jammed, it could sound like what you shared.

Be sure to report back what you find.