An electric assist choke is used on 4-bbl carburetors to more accurately match the choke operation to engine requirements. It provides extra heat to the choke bimetal spring to speed up the choke valve opening after the underhood air temperature reaches 95ºF±15ºF. Its purpose is to reduce the emission of carbon monoxide (CO) during the engine's warmup period.
A special AC terminal is provided at the alternator to supply a 7 volt power source for the electric choke. A thermostatic switch within the choke cover closes when the underhood air temperature reaches 95ºF±15ºF and allows current to flow to a ceramic heating element. The circuit is completed through the choke cover ground strap and choke housing to the engine. As the heating element warms up, heat is absorbed by an attached metal plate which in turn heats the coke bimetal spring.
After the engine is turned OFF, the thermostatic switch remains closed until the underhood temperature drops below approximately 65ºF. Therefore, the heating element will immediately begin warming up when the engine is restarted, if the underhood temperature is above 65ºF.