RV Repair: Vibration in new DuoTherm Peguin A/C, grating sound, vibration noise

Question
On my 2008 RV the front AC unit (13500 BTU) exhibits a cyclic vibration noise (very irritating) when the compressor is running.  No vibration when fan alone runs.  Vibration coming from evaporator unit.  Pressing my ear to the evaporator enclosure reveals that the cyclic grating sound is definitely coming from this portion of the AC unit.

Answer
Hi Joe. How loud is it? All roof and basement AC's make a harmonic vibration noise that is definitely noticeable. You say front AC, so I assume you have another AC to compare it to. If you have a noise that is not like the rear, and its a 08. I would have I replaced under warrantee. Good Luck.