Gus, When starting the car and everything is right, the voltage will drop to about 10.25 volts. If you run the voltage thru the complete resistor you will have more voltage drop and harder to start the car. So: This relay transfers the voltage from the solenoid to the left side of the resistor cutting out 1/2 of the resistor during starting for more starting power. Some cars didn't have the relay, the solenoid wire was hooked directly to the left side of the resistor. Either way it will work. On My special HV coil and resistor, I go directly to the right side of the resistor, which again gives me more starting power. John hervey http://www.specialtauto.com/ << Can anybody tell me the purpose and part number for the silver colored relay that is located back of the engine on the firewall about 8 inches left of the ignition resistor? >>