I don't use a bulb for the charing system. You can use the bulb if you like (in addition to the resistor). The resistor has to be connected to both wires as does the bulb. If I remember correctly they are lg/r and r/lg. The wires are 2 different sizes and go to the cluster. I have found a bulb from a 1987 Mustang works the best. The Ford part # is E6DZ-13B765-B and cost around $5. The resistor is built into a bulb holder. Pull the bulb out and solder the wires to the terminals. I used the Radio Shack part on 2 cars and both of them broke over time.
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