Bob R. 7/7/2010There's no heat sensor for the A/C clutch itself. It sounds like you may have a bad compressor that is overloading the clutch. See if you can turn the compressor by hand - not the clutch, which should turn easily without the belt on - but the A/C compressor itself. It should turn with moderate effort.
Another clue to a bad compressor would be a belt that is badly glazed, or the engine spead decreasing considerable just as the A/C clutch engages.