The weird thing is though the noise only comes on under 2000rpm in any gear. Once over 2000rpm there is no noise at all.

 

i know i'm bringing back an old thread. but i also have this under 2000rpm problem. does anyone know what it could be?

 

It actually sounds like the alternator belt that makes the noise or at least on my car.

 

I'm hearing a high pitched whir around my AC compressor when I hit 2500 RPM and have to shift up to avoid the sound. Seems to be the pulley that connects to the belt, which means I would have to replace the entire compressor which pumps AC just fine. How do I know if I need to replace the compressor or just the belt?

 

When you turn on the defroster does the ac compressor clutch engage every now and then, or is it constantly engaged?

 

When I turn on the defroster it is constantly engaged. Is that good news?

 

Unfortunately no, that's not good news. After being used so much the ac compressor clutch plate stays engaged, which keeps it on constantly. The plate gets magnetized to engage the ac and after a while it just stays magnetized, you probably have some metal shavings in between the base of the pulley and the compressor, or worst case scenario the refrigerant seeped out of the system and the compressor is constantly running unoiled which will cause it to seize up and shred your serpentine belt. I'd recommend taking it to a shop that specializes in auto ac work and tell them the problem. I had the same problem on an old chevy cavalier of mine, cost me $90 to have it fixed.