Sounds like a short in the AC clutch or the wiring leading up to it.
To make a quick diagnosis of which, pull the plug off the AC clutch,
then replace the fuse and then try and turn the AC on by pushing the
AC-ON-OFF switch in to the on position.  If the indicator lights up
and the fuse doesn't blow you know the problem is in the clutch since
it's the only part not connected.  If the fuse still blows, it's
something other then the clutch that's shorted.  While you are
monkeying around under the hood to disconnect the wire take a look at
the wiring and see if there is an obvious spot worn thru and shorting
out.