Where is the heater control valve in a 1998 Volvo S90?

In a 1998 Volvo S90, the heater control valve is typically located in the engine compartment, near the firewall on the passenger side. It is connected to the heater hoses that run to the heater core. To access it, you may need to remove some components or covers, depending on the specific layout of the engine bay. Always consult the vehicle's service manual for precise location and access instructions.