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9. TEST APPLICATIONS
9.8 CHECKING FOR BAD GROUND CONTACTS
Probe the suspected ground wire or contact with the probe tip.
Observe the green LED. Depress the power switch forward then release. If the green LED went
out and the red LED came on, a beep will sound, this is not a true ground. If the circuit breaker
tripped, this circuit is more than likely a good ground. Keep in mind that high current components
such as starter motors will also trip the circuit breaker.
9.9 FOLLOWING & LOCATING SHORT CIRCUITS
In most cases a short circuit will appear by a fuse or a fusible link blowing or an electrical
protection device tripping (i.e., a circuit breaker). This is the best place to begin the search.
Remove the blown fuse from the fuse box.
Use the probe tip to activate and energize each of the fuse contacts. The contact which trips the
circuit breaker is the shorted circuit. Take note of this wire’s identification code or colour.
Follow the wire as far as you can along the wiring harness.
Here is an example for this application.
• If you are following a short in the brake light circuit, you may know that the wire must pass
through the wiring harness at the door sill. Locate the colour-coded wire in the harness and
expose it.
• Probe through the insulation with the probe tip, and depress the power switch forward to activate
and energize the wire.
If the circuit breaker tripped, you have verified the shorted wire. Cut the wire and energize each
end with the probe tip. The wire end which trips the circuit breaker again is the shorted circuit and it
will lead you to the shorted area.
Follow the wire in the shorted direction and repeat this process until the short is located.
9.10 RED/GREEN POLARITY LED
The Red/Green Polarity LED lights up when the probe tip voltage matches the battery voltage
within ±0.4 volts. It is added information that could be valuable to the technician.
If the circuit you are testing is not within a 0.4 volt (plus or minus) of supply voltage, you will see
the voltage reading on the LCD but you will not hear a tone or see a red or green LED. This tells
you either you have a voltage drop in excess of 0.8 volt from battery voltage or you are probing a
circuit that has an increase of a 0.8 volt or more over battery voltage. To determine battery voltage,
simply remove the tip from the circuit and press the power switch forward. Battery voltage will then
be displayed on the LCD. The difference between the battery voltage and what is read on the
circuit is either voltage drop or voltage increase. This allows you to determine a voltage drop
without running back to check the battery. It’s just another one of time saving feature the tool has.
