Got out to open a gate and left my 96 Dodge Cummins Automatic in park with the A/C running. I heard a periodic chirping noise coming from, I think, the serpentine belt area about every 30 seconds or so. Later I turned off the A/C and let it idle in park and did not hear the noise.

Any ideas?

 

A/C clutch is the culprit. Mine has been chirping also, so I got under and looked the clutch springs are broken and the bearing is very loose.

 

Is the A/C clutch and fan clutch the same or different?

 

Birds nest with baby chicks in it. All gone now......

 

No, fan clutch is on the fan and is activated by a thermo/bimetallic spring. A/C clutch is mounted to the front of the A/C compressor and is engaged by an electric current engaging electromagnetic coupler

 

It's probably just the belt. I can't seem to find a belt that doesn't start making noise after 2 months or so.