Weird noise is being made wen i trn my ac on from 3 and switch it up to 4.also the loud weird noise only is heard when my engine is running...what might this be and how can i get it fixed.the noise comes from the passenger seat.under the glove compartment...

 

Is the noise a "screech" that is piercing? If yes, the blower armature is wobbling and hitting the field magnets? This produces are very loud screech.

If noise is softer, rattling, whirring sound it may be worn carbon brushes jumping up/down in the holder. This is a warning of imminent failure of the brushes usually, but no harm in waiting until they fail.

In both cases, a new blower motor is fix.

good luck