Thermostat is a device for maintaining a static (constant) temperature, as its name implies. There are thermostats of different designs in many devices and mechanisms, from water heaters to refrigerators. There is also a thermostat in a car's internal combustion engine (liquid-cooled, of course). In a car, the thermostat regulates the temperature of the coolant (antifreeze): it accelerates the warm-up of a cold engine and provides heat removal from the hot one. Therefore, the engine works more efficiently and more comfortably for the driver, especially in winter - without a thermostat, the stove would usually blew cold air.

1. A4 (8E2, B6)
2. A4 / S4 (8E2, B6)
3. A4 Avant (8E5, B6)
4. A4 / S4 Avant (8E5, B6)
5. A4 (8EC, B7)
6. A4 Saloon (8EC, B7)
7. A4 / S4 (8EC, B7)
8. A4 Avant (8ED, B7)
9. A4 / S4 Avant (8ED, B7)
10. EXEO (3R2)
11. EXEO ST (3R5)
12. See more in applications

The principle of the thermostat work

The classic HOFFER brand Thermostat, coolant is a movable valve that moves due to a change in the external environment - heating or cooling of antifreeze. The thermostat is made of a thermoelement filled with a substance resembling wax in structure - ceresin, with the addition of copper powder, graphite or aluminum for better thermal conductivity. At a certain temperature of the antifreeze, ceresin expands, opening the thermostat valve. When the motor cools down, ceresin contracts and the thermostat closes again.