How do I replace the thermostat on a Volkswagen fox?

To replace the thermostat on a Volkswagen Fox, first, ensure the engine is cool and disconnect the negative battery terminal. Drain the coolant and remove the hoses connected to the thermostat housing. Unbolt the thermostat housing, replace the old thermostat with a new one, ensuring the gasket is in place, then reassemble the housing and hoses. Finally, refill the coolant and check for leaks before reconnecting the battery.