How do i change the heater controls under the dashboard on 1999 Hyundai excel?

To change the heater controls under the dashboard on a 1999 Hyundai Excel, first, disconnect the negative battery terminal to ensure safety. Remove the dashboard panel by unscrewing any screws and carefully prying it off. Once exposed, locate the heater control unit, disconnect the electrical connectors, and remove any screws holding it in place. Replace it with the new unit, reconnect everything, and reassemble the dashboard.