I'm not sure if this is normal for 2.5l TJs, but whenever the A/C is on and turned to cold you can here a kind of additional drone, whirring type noise at certain RPMs. For example, when accelerating I notice the additional sound, as well as hampered acceleration speed, but I turn it off and acceleration feels normal again and the sound doesn't appear either. The same sound happens when just revving the engine in neutral as well. Is this normal or is there an issue with the A/C compressor or is it something else?