Choke Thermostat/Heater: Description and Operation

Fig. 39 Electric Choke assembly exploded view:

The electric assist choke is designed to give a more rapid choke opening at temperatures above 60° to 65° F and a slower choke opening when temperatures are below 60° to 65° F.
The electric assist choke system does not change any carburetor service procedures and cannot be adjusted. If system is found out of calibration, the choke unit must be replaced.
The main components of the system, Fig. 39, consist of the thermostatic coil, ceramic resistor, cover, bi-metal snap disc and contact spring. The ceramic resistor is divided into a small center section for gradual heating and a larger outer section for rapid heating of the thermostatic coil. The electric actuated ceramic resistor heats the thermostatic coil, gradually relaxing coil tension and allowing the choke valve to open.
At air temperatures below 50° F, electric current applied to the small section of the ceramic resistor, allows slow opening of the choke valve for goodengine warm-up. As the small section of the ceramic resistor continues to heat, a bi-metal disc causes the spring loaded contact to close and apply electric current to the large section of the ceramic resistor which increases the heat flow to the thermostatic coil for more rapid opening of the choke valve.
At air temperatures between 50-70° F, electric current applied to the small section, or both the small and large sections of the ceramic resistor, will produce the amount of heat required to control the choke valve position for good engine operation in these temperature ranges.
At air temperatures above 70° F, electric current applied to the small section of the ceramic resistor and through the spring contact to the large section of the ceramic resistor, provides rapid heating of the thermostatic coil for quicker choke valve opening when leaner air/fuel mixtures are required at warmer temperatures.