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How to Trace out an Open Circuit:
An open circuit does not complete a path to ground. The cause for an open circuit can vary from an open switch, unplugged connector, bad con-
nections and breaks in wires.
1. Connect the transmitter’s power lead to the vehicle’s battery.
2. Connect the SMART transmitter’s signal lead to the open circuit.
3. Turn on the receiver. It will be in “pulse mode”.
4. Place the “Open & Short Pick-Up” near and parallel to the open wire until the “Open Circuit” LED indicator blinks and beeps. (be careful to
hold the receiver from the outer edge to prevent your hand from shielding the signal)
5. Lift receiver away from the open circuit so that the pulse of the “Open Circuit” indicator slows down but doesn’t stop completely.
6. Press the “Sense Lock/Sense Low” button.
7. Hold the receiver near to the open circuit and while the “Open Circuit” indicator is ON steady, follow the path of the circuit or wire until you
lose the signal.
8. If you reach an obstacle, remove it or work through it. Remember to ISOLATE THE CIRCUIT YOU ARE TRACING. Inspect the circuit
and verify the open circuit. (See” “Verify an Open Circuit” below.)
9. Continue Steps 7-8 until you find the open or break in the circuit.
Verify an Open Circuit:
One of the best methods for verifying an open circuit is using a Power Probe circuit
tester together with the transmitter. Since the transmitter’s open circuit signal delivers
8 volts and a 4 kHz signal, it can be easily detected by directly contacting the Power
Probe III or IVto the wire of the transmitting circuit.
Contact the probe of the Power Probe III or IV to the open circuit with the open circuit
signal applied to it. You should hear the 4 kHz tone from the Power Probe III speaker.
If you don’t hear the 4 kHz tone, inspect the circuit closer to determine why. If you
hear the 4 kHz tone, you are on the correct circuit.Testing the open circuit with trans-
mitter together with the Power Probe III has advantages over just a continuity test.
This is because the transmitter’s toggle tone feature will alert you if the open circuit
makes contact with an intermittent grounded circuit.
(See: “Circuit Wiggle & Flex Test” pg. 26)
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