A first air pump itself a gap if the gap is relatively large, it becomes the impact is large, it will result in sound. 

Another point is the tightness of the need for regular air conditioning belt adjustment, re-adjust the air conditioning belt, see if you can solve. 

Because the third time is relatively long, cooling air-conditioning in itself is not particularly good, has some influence on the pressure of the air conditioning system, especially for air conditioning starts instantly influential. 

Should not affect normal use, this situation occurs, it is recommended to check the service station.