Generally, humming sounds aren't dangerous, but it still indicates that your air conditioner is malfunctioning.  It is not uncommon for loose parts and refrigerant lines to cause vibrations, leading to a more serious maintenance issue if not addressed by a professional. If the system is humming or buzzing, it could also be an electrical issue. Get in contact with us today should you have any questions or concerns at Sharp Air Conditioning & Heating, LLC. Call  us at (480) 695-7834 for air conditioning repair Mesa.