Whistling new compressor

So I had my AC go out in my 2007 Honda Civic coup and being a cheap guy, didn’t want to pay the mechanic 1200-1300 bucks to fix it and all the peripherals (condenser, desiccant, expansion valve, hoses…) So I bought all of the stuff myself for about $500 (Reman compressor) and took it to a mechanic buddy that owed me a favor. We took out the compressor and checked the movement of the pulley wheel and it moved freely. He informed me that it was just the clutch on the compressor that was bad and the rest of the stuff didn’t need replacing. So we swapped out the new for the old compressor put it all back together charged it and glorious cold air blew in abundance. Once I hit the road, I noticed a whistling sound that occurs while accelerating through about any speed. It is not a belt squeak and it’s not the “whistling between 40-50 mph” like the service bulletin on the 2006-2008 CR-V. It occurs as low as 20 mph and up to 80 mph.

My questions are these: is this a symptom of a problem which needs attention? and: What did my buddy do wrong?

Does the whistling happen when AC is off, too? Or only when it’s on?

just when it’s on. as soon as I turn off the AC, the whistling stops.