I'm assuming your not an elevator contractor by your description, most elevator men use different terminology. To answer your question, it's always a good idea when one contact needs replacing on main contactors to replace all of them. You should have a skilled person do this, they can tell alot by checking the wear of all contacts (may have something going on causing only one to burn). Also, depending on style of contactor your talking about, the wipe, pick-up, tension and other factors have to be adjusted for proper operation. If not done properly you good be looking at causing safety issues or lose a motor.
