With the A/C off, the car sounds normal. With the A/C on, there is an intermittent chirping or squealing noise.
The photograph shows the A/C compressor. In the middle of the pulley attached to the compressor is a "triangle." With the A/C off, the triangle does not spin and there is no noise. The pulley does rotate, but the triangle does not. With the A/C on, the pulley rotates and the triangle does move, but does not move at the same rate as the pulley. It seems to "lag" or to be unable to keep up.
The triangle can be spun freely by hand with the motor off. I'd expect this anyway though, since the electromagnet is not engaged, right?
Belt tension "seems" normal by hand (the maximum deflection at the midpoint of the belt is less than the width of the belt -- crude measure but that's what I've got).
So... Belt problem (my hope)? Clutch problem (second best scenario)? Compressor problem (worst ca$e $cenario)? Something even worse than that?
All help appreciated, as are any suggestions for parts sources (I checked the dealer price for a compre$$or in case I need one, and it was "ouch").