You can pull the HVAC blower motor out and inspect it.
SOmetimes moisture will seep into the motor area of the HVAC..and cause it to rust.. thus..depending on speed of motor will make all sorts of annoying sounds.. Mine ended up rusting out and was squeaky..as hell until it finally just stopped working.. So i had to replace it..
You can remove the HVAC motor.. by looking directly under the passenger side dash...remoce the cladding..underdash than remove 3 bolts/...you will need to disconnect the wiring harness from the hvac motor..than just pull down and out..