I have a 2006 Kia Optima it runs fine, but whenever I turn on the air conditioner the car vibrates. The motor mounts have been installed and the air conditioner has been checked. Is this something I have to live with or is this something that can be fixed. The last mechanic put in a new radiator the old one was leaking) and he said the vibration is common to old Kia models.
An A/C system can put a lot of load on an engine. Some cars react differently to it.