How do you replace heater valve on Volvo 940?

To replace the heater valve on a Volvo 940, first, disconnect the negative battery terminal and drain the cooling system. Then, locate the heater valve, which is typically found on the firewall near the passenger side. Remove the hoses connected to the valve, then unbolt it from its mounting. Install the new valve by reversing the process, ensuring all connections are secure, and refill the cooling system before reconnecting the battery.