458 AC Compressor

If the bearings in the compressor are burnt up, it will simply mechanically seize and eat the belt. I haven't had that happen in a long time but it can definitely happen, especially if the system leaks since most compressors need lubricant in the refrigerant.

 

With the AC set to off the clutch will be disconnected and you should be able to turn the belt pulley by hand, if the belt is off. You should also be able to run the engine with the belt on and AC selected as off.
With ref to being able to turn the compressor by hand with the AC off, i would think not as the pumping part is still under pressure- when the compressor is running you have suction and discharge pressure- when the AC is off the clutch disconnects and over time the discharge pressure will drop and the suction rises until they are equal.
Have you tried fitting a belt, then starting engine with AC off- then switch AC on- any noise from the belt or burning smell ?

 

How did you get on ?

 

They can lockup due to lack of oil, as the gas is pumped around the system it has an oil mist mixed in the gas to lubricate the compressor as it passes through it. Other reason could be loss of gas and the low pressure gas switch not working, so it seized up. I assume they tested the low pressure cut out switch when they fitted the new compressor

 

My independent is replacing my compressor/evap valve/pressureswitch/drier as a precaution (I've been running low on ac refrigerant and the a/c was pretty awful on anything other than MAX cool setting).

I've had an ac compressor go out on my before in Hong Kong and it is NOT a pretty situation to ever be in.

My car is just over 10 years old so I really don't care whether I "need" or right now as there's a high chance I'm gonna need it in the next few years anyways so figure get it done while he's in there.

 

I always turn my air condition on every outing as I feel it lubes bearing etc. I do this for approx. ten minutes into the rides.