Thermo Time Switch: Description and Operation

Fig. 21 Thermo-time switch:

The thermo-time switch, Fig. 21, controls opening time of the cold start valve; it is affected by starter current and coolant temperature.
The thermo-time switch consists of a bi-metallic strip, heating coil, and contacts which are connected to an external plug.
Depending on coolant temperature conducted through the switch housing, the heater coil takes from 3 to 10 seconds to deflect the bi-metallic strip and open the contact points during starting. Opening the points interrupts the ground circuit of the cold start valve.
The bi-metallic strip and contacts within the switch are connected to the ground side of the cold start valve, and the heating cable is connected to terminal 50 of the starter circuit. This ensures that the cold start operates only for a short time during starting.