It would be best to consult your owner's guide to see about the operation of the ventilation controls. It is possible that even with the controls off, that it allows ventilated air flow to continue. There may be a method of turning this off, such as setting the air flow to "recirculate" - thus, not allowing in outside air.
RepairPal Certified shops can diagnose and repair your 2004 Hyundai XG350. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.
