Thermal switch manufactured by German brand Wahler. Controls coolant fan speed at the lower speed coming on at 95 degrees C and turning off at 84 degrees C and the second higher speed coming on at 102 degrees C and turning off at 91 degrees C. Fits A3 Jettas and B4 Passats plus 1999.5 A4 chassis TDIs. 3 pin housing style is square shaped.