Operating principle of the automatic starting device (BMW 3 Series E21)

The principle of operation of the automatic starting device is based on the supply of current to a bimetallic spring enclosed in screen 64, which, as it heats up, acts on lever D, connected by adjustable rod 42 to the drive of the throttle valve of the 1st chamber, and also on the use of heat from the cooling liquid circulating through the tubes in liquid chamber 66. A sealing gasket 65 is installed between the liquid chamber and the housing of the bimetallic spring.

When the engine starts, the electrical circuit of the bimetallic spring closes and it quickly heats up.

At a coolant temperature of 80-90°C, the thermoelectric sensor opens the power supply circuit of the bimetallic spring, the temperature of which is then maintained only by the circulation of hot coolant.

(The original entry can be found on the portal BMWman.ru)