Thought this might be of interest to anyone who thinks something may be wrong with their Macbook Air's and wants to run the Apple Diagnostics. I had to take my Air back to the Regent Street store as the exhaust fan had failed according to the iStat Pro widget. 0 RPM and 73c. Before they would swap it out the genius ran the apple diagnostics by holding down D then the power button it then must load the diag program from a hidden partition on the disk. The diag failed on the exhaust fan I then got my replacement.