Checked the Changeair self contained unit #16 for no cool. Found one of three fuses blown to the compressor contactor. Replaced the fuse and started the unit. Verified operation and checked for the cause of the fuse failure. Staff advised that the unit was making a chattering noise before it stopped cooling. Was not able to duplicate the chattering while on site. Bypassed the freeze stat and low pressure switch for testing. Will check back tomorrow the verify operation.