Nissan Almera can i uncouple aircon?

My aircon stopped working some time ago and when the car was serviced, the garage told me it would need a new aircon unit. I decided I could do without aircon as it was very expensive and the heater/cold air works without zircon. Yesterday the car started making a horrendous noise under the bonnet, really loud. I took it to the garage and they quoted £466 to fit a new unit but said in the meantime keeping both the aircon button and the fan running would stop the noise. Which it does, more or less. My question is firstly will this do the engine any damage and secondly, can I just detach the outer wheel (the one that's making the noise) from the inner wheel (the one that doesn't work)? The car is old but has low mileage.