Power Probe ECT 2000 - Manual (Page 18)

18
Isolate the Circuit You are Tracing
Isolating the circuit you want to trace is absolutely necessary when
using “Open Circuit Signals”. It is always good to disconnect the
circuit you are tracing away from other parallel circuits. Once you
isolate the troubled circuit, you can then connect the SMART trans-
mitter’s signal lead exclusively to your selected circuit. Connecting
exclusively to your ISOLATED circuit insures that the SIGNAL is
confi ned in just that one single circuit. The signal strength remains
constant throughout the isolated circuit. This makes the circuit
easier to trace. You also eliminate confusion of the signal branching
off to other areas that will lead you astray. When you are fi nished
diagnosing, don’t forget to reconnect the isolated circuit.
Verify a Short Circuit to Ground
One of the best tools for verifying a short circuit to ground is the
Power Probe 1, 2, or 3. To verify a short circuit connect the Power
Probe to the circuit and press the power switch forward. If the Power
Probe’s circuit breaker trips, you have verifi ed the short.
Be careful not to power up circuits that are connected to the vehicles onboard
computer. You may have to unplug the computer or electronic modules when
performing short circuit verifi cation on electronic systems.
Fig. 1
Fig. 2
Problem circuit not isolated
Disconnected
from circuit
These circuits are no longer
a problem because they are
disconnected from the
problem circuit.
Signals are
all over the
place, because
the problem
circuit has not
been isolated
Signal injected directly
into the problem circuit.
Isolating a short/grounded circuit is best done by removing the
loads in the circuit. This accomplishes two things: 1. It assures
that 100% of the signal is being transmitted down the wire you are
tracing, 2. if the circuit goes intermittent, the transmitter will alert
you. (See: “Circuit Wiggle & Flex Test” pg. 26)