The Stovebolt Site Forums The Shop Area The Electrical Bay Confused... 12V conversion

I know this subject has been beaten to death several times over... But I'm CONFUSED

First...

If you change to a 12V coil, why do you need a resistor between it and the points???

Why do you need seperate reducers for each item in the truck? why couldn't you just reduce it once and then feed everything off of it?

Question 1 answer: To extend the life of the points.

Question 2 answer: Your radio and heater blower are high amperage and your fuel guage is low amperage. The fuel guage takes a different type of reducer to work properly.

An alternative to reducers is a battery with a 6V tap on it. All 6V accessories can then run off the tap.

The ballast resistor doesn't go between the coil and the points. It goes between the coil and the source voltage(ignition switch). A direct 12 V source, usually the starter solenoid, bypasses the resistor to supply the coil with 12 V for starting only.

The design that Richard explains was an opportunity to improve the starting voltage. On the 12 v systems, the resistor was bypassed by the solenoid when starting, making up for some of the drain on the system voltage. I believe that you can buy 12v coils that don't need the resistor. If you are using the foot type starter, the resistor type of coil would not be of any advantage.

There are a number of types of reducers. I think that you can get 12v replacement motors for the fan but I don't know about the gas gauge.

During some starting situations, the load of the starter motor will drop the battery voltage to about 9.5 volts. Using a coil that needs 12V to fire well results in a weak spark during a cold start when you need a good one. By using a coil that works on 9 volts, and dropping the voltage from 12 to 9 during normal running, then bypassing the resistor during starting, you get a good spark all the time.
Jerry

I remember some 12v coils also have an internal resistor built into it,(6v to points regardless) just depends on the system. Some had two circuits to the coil 12v for starting then with the resistor 6v to coil (that used to be chyrslers i think?) Some later chevys and others also used a resistor wire that ended up being a fusible link also... points will run on 12v they just wont last very long,,,, also.. if ya leave the ignition switch on the points will burn without it even running if the points are closed. Thats why they used the accessory side of the switch to apply voltage to things ya might wanna use like the radio without the car running...if ya left the ignition on for awhile it would melt the points........