How do you replace a heater control valve on 1995 GMC Vandura?

To replace the heater control valve on a 1995 GMC Vandura, first, ensure the engine is cool and disconnect the negative battery cable. Drain the coolant from the radiator, then locate the heater control valve, typically found near the firewall. Disconnect the hoses and electrical connections, remove the mounting bolts, and take out the old valve. Install the new valve by reversing the removal process, secure everything, refill the coolant, and reconnect the battery.