Range Rover County LWB (LH) V8-4.2L (1993)
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To locate an open circuit, a voltmeter or LED test light can be used. To check a portion of the circuit for continuity, an ohmmeter or self-powered test
light can be used, but only after the circuit has been disconnected to remove the voltage. A jumper wire can also be used to bypass portions of the circuit
in an attempt to make it operational. If it becomes operational with a jumper wire installed, that portion of the circuit jumped is open.
In a normally operating circuit, such as the simple parallel circuit shown, the left branch is receiving power. Current is flowing through lamps "One" and
"Two". If tested with a voltmeter, the circuit would read 12 Volts on the "HOT" side and 0 Voltage on the "GROUND" side. Because the right branch of
the parallel circuit is open at the switch, it is not powered.
If an open occurs in the ground side of the powered branch, as shown, the continuous path for electricity is broken. As a result, no current flows. Voltage
will be at 12 Volts at all parts of the circuit between the power source and the open.
The lesson to be learned from this example is that in a simple series or a simple parallel circuit, no current will flow when it is open. All points that are
connected to the power source will be at battery voltage.
In more complex circuits, however, opens often have different effects on voltage and current. The view, as shown, is a variation of the previously shown
circuits. When this circuit is operating normally, lamps "One" and "Three" are powered when the switch is in the position shown.