This Preliminary Information communication provides information to the technician about vehicles that may have an oily substance is found on the inside windshield surface and appears to be leaking from the rear view mirror area. Technician should inspect the moisture sensor for being the source of the leak, if found to be leaking, carefully remove the moisture sensor. Clean the glass surface and sensor bracket with an isopropanol alcohol wipe until the surfaces are clean, then re-install the moisture sensor.