How do you replace a heater matrix in a 2001 corsa?

To replace the heater matrix in a 2001 Corsa, start by disconnecting the battery and draining the cooling system. Remove the dashboard and associated trim to access the heater unit, then disconnect the hoses and electrical connections from the matrix. After unbolting the heater unit, extract the old matrix and install the new one, ensuring all connections are secure. Finally, reassemble the dashboard, refill the cooling system, and check for leaks.