Originally posted by just a six:
A ballast resistor is designed to drop the voltage as current flows through it. The reason it does this is the resistor "coil" uses a specific type of wire that does not pass all of the electricity going into it. As part of the current is blocked, so to speak, heat is accumulated in the wire as a byproduct of the wire resistance. An example of this phenomenon is any heating element such as a stove burner or toaster element. If there is not enough current, then there will be no voltage drop. As a rule, guages use very little current and therefore can't use a ballast resistor. Those are designed for ignition coils that will use anywhere from 10 to 100 times the current of a guage.
What you ought to use is an electronic voltage reducer kit specifically designed to do what you want. I've seen them advertised for years in J. C. Whitney catalogs and other suppliers like that.
Do the instructions in the Car Shop kit say to wire it up as you've described? You will need to connect some load to it to test the system, but I get the feeling you probably shouldn't use your newly-restored gauges.
Hope this helps. Anybody else used a Car Shop kit?
