I've seen quite a few XR11 / XR12 recently with bent fan shrouds (that top piece that the condenser fan motor mounts to). When the fan starts (or stops) the edge of the shroud vibrates down on the top frame to which it is mounted and causes a 'bang'. Also check the plastic trim piece in the center of the shroud to make sure it is not rattling.Originally posted by seabreeze
Did he say anything about the noisy start and stop. My XR11 (less than a year old) still makes a sound when starting up like the fan is out of alignment or a bearing is going bad. Once it gets going its ok but shutdown is not quiet either. Not sure whether to call in installer or live with it.
If the fan shroud is the problem and replacing it isn't an option you can just remove it temporarily (4 screws) and put a narrow (1/2") piece of thin weatherstrip tape all the way around the top frame. Then remount the shroud. Probably not a factory approved work around but it seems to do the job.