Handbook 652 Body Electrical Diagnosis Open Circuit Voltage Voltage measured when current is not flowing in the circuit is called open circuit voltage. The reason current would not be flowing is because of an open in the circuit disrupting the path for current flow back to the voltage source. An open can be caused by a switch or other control device in the open position, or a break or disconnection in the wiring or connectors. With an open in the circuit: • Voltage measured anywhere in the circuit before the open (power side) will be equal to source voltage. • Voltage measured anywhere in the circuit after the open (ground side) will be zero volts.
HINT If you are measuring voltage in a circuit that is not operating and find source voltage at one test point and zero volts at another test point, the open in the circuit is between the two test points. Technical Training 19