1、OE Number: The referencing OE number of this heater control water valve are 4H0121671D, 4H0121671B, which is molded and designed depend on the original data. 2、Fitment: The AC heater cooling solenoid valve is a replacement for A3 A4 Allroad A5 A6 A7 Q3 Q5 Q7 Q8 RS6 RS7 Sportback RSQ8 S3 S6 S7 S8. 3、Function: Regulate the amount of hot coolant that flows into the heater core, allowing for precise control of the temperature inside the car. 4、Energy Efficient: By controlling the amount of hot coolant that enters the heater core, the valve can help to save energy and lower fuel costs. 5、Ideal Replacement: Direct replacement installation, original style, meets or exceeds OEM standards for the replacement of old and damaged one.