Thermo Time Switch: Description and Operation

The thermotime switch is incorporated into the thermostat housing. A harness is connected to the cold start valve from the thermotime switch. The bi-metal contact in the thermotime switch opens or closes depending on the cooling water temperature, and sends a signal to the cold start valve so an additional amount of fuel can be injected for cranking operation of the engine when the cooling water temperature is below 57-72°F. The thermotime switch is ``On'' when the cooling water temperature is below 57-72°F. However, repeated operation of the ignition switch may result in excessively rich mixture. To prevent the rich mixture the bi-metal is equipped with a heater. Electric current flows through the heater when the ignition switch is in the start position, and heats the bi-metal. Through repeated operation of the ignition switch, then, the bi-metal is sufficiently heated to open the thermotime switch, stopping excessive injection of fuel from the cold start valve.