How an electric Choke works
zanblackrain
Jeeper
I found this on another forum and it helped me with my issue. So i would like to share for anyone else who is having an issue with there choke.
1980 CJ5 AMC 258 i6 / 4.2l ci 4 speed
Here is how the electric choke works.
There is a flat coil spring under the black plastic cap on the choke mechanism. One end of the spring is anchored to the plastic cap and the other end of the spring is attached to the choke shaft. The cap can thus be rotated to open or close the choke. The spring is a special material called 'bi-metal'. It is made of two metal alloys that are bonded to each other and have widely different thermal expansion values. All metals expand when they are heated and these two metals expand at different rates so as the spring gets hot, it tends to unwind as one surface gets longer than the other. When the spring cools, it winds back. If controlled, this winding and unwinding could be used to rotate a shaft as in a carburetor choke. This is exactly how your automatic choke is working. The 12V wire you connected to the choke heats a resistance heater that is enclosed in the choke housing next to the bi-metal spring. When you turn your key to 'RUN', the resistance heater begins to warm the spring and the choke slowly opens. You can adjust the opening time by turning the cap and loading or unloading the spring closing force on the choke.
Bi-metals are used in many every day items. Hair dryers and heat guns use them as a safety switch. If you have ever been using one of these tools and it suddenly turned off, then began to work again after a wait, that was a b-metal safety switch opening the power circuit when it got to a potentially dangerous temperature. The click, click, click you hear when you actuate the turn signal in your car is another bi-metal switch in action. Rather than being a slow responding switch or spring as in the previous two examples, it is a rapid acting device so it will cycle fast enough to act as a flashing switch. There is a resistance wire coil wrapped around the bi-metal and the turn signal current flows through it heating it but when the switch opens, it breaks the heating current (and lamp current) and the bi-metal quickly cools and the switch closes, restoring the heating and lighting circuit. If you have a taillight burned out; there is less current flowing through the heating coil. That is why the flasher will slow or sometimes even quit flashing when a bulb is burned. Have you ever changes a flasher thinking it was bad to find the new flasher didn't work either? Problem wasn't the flasher; it was the burned out taillight that starved the flasher of proper heating current!
1980 CJ5 AMC 258 i6 / 4.2l ci 4 speed
Here is how the electric choke works.
There is a flat coil spring under the black plastic cap on the choke mechanism. One end of the spring is anchored to the plastic cap and the other end of the spring is attached to the choke shaft. The cap can thus be rotated to open or close the choke. The spring is a special material called 'bi-metal'. It is made of two metal alloys that are bonded to each other and have widely different thermal expansion values. All metals expand when they are heated and these two metals expand at different rates so as the spring gets hot, it tends to unwind as one surface gets longer than the other. When the spring cools, it winds back. If controlled, this winding and unwinding could be used to rotate a shaft as in a carburetor choke. This is exactly how your automatic choke is working. The 12V wire you connected to the choke heats a resistance heater that is enclosed in the choke housing next to the bi-metal spring. When you turn your key to 'RUN', the resistance heater begins to warm the spring and the choke slowly opens. You can adjust the opening time by turning the cap and loading or unloading the spring closing force on the choke.
Bi-metals are used in many every day items. Hair dryers and heat guns use them as a safety switch. If you have ever been using one of these tools and it suddenly turned off, then began to work again after a wait, that was a b-metal safety switch opening the power circuit when it got to a potentially dangerous temperature. The click, click, click you hear when you actuate the turn signal in your car is another bi-metal switch in action. Rather than being a slow responding switch or spring as in the previous two examples, it is a rapid acting device so it will cycle fast enough to act as a flashing switch. There is a resistance wire coil wrapped around the bi-metal and the turn signal current flows through it heating it but when the switch opens, it breaks the heating current (and lamp current) and the bi-metal quickly cools and the switch closes, restoring the heating and lighting circuit. If you have a taillight burned out; there is less current flowing through the heating coil. That is why the flasher will slow or sometimes even quit flashing when a bulb is burned. Have you ever changes a flasher thinking it was bad to find the new flasher didn't work either? Problem wasn't the flasher; it was the burned out taillight that starved the flasher of proper heating current!
Mike S.