I've noticed when I turn on the A/C and start to accelerate, I hear a groaning fan like noise. As soon as I turn off the A/C button the noise stops. When the car was in factory warranty, the dealer ended up replacing the A/C unit and I still hear the noise. Could it be the fan? I assume that I would receive an error code if it was truly something. Thoughts?

Thanks.

I checked with my import shop and it sounds like the compressor staging the a/c unit.

My ML does the exact same thing....dealer said it was normal.