General Technologies FF300 Fault Finder for Electrical Wiring Open / Short Circuit - Manual (Page 6)

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12.3 Some circuit characteristics that may affect the tracing of a wire:
• Electromagnetic loop size and geometry, etc. may affect the range of the
FF300’s. For example for circuits in which the live and ground (return) wire run
parallel and close to each other in the same circuit. The two magnetic fields
interaction may weaken the signal, thereby reducing the FF300 range.
•
Wires enclosed or tightly lining the metal frame or body of the vehicle, (i.e.:
door frames, etc.), have the same effects as having the live and ground wires
running in parallel in the same circuit since, the metal frame or vehicle body will
be acting as a ground wire. Another unfavorable factor may be due to the chan-
neling effect steel parts have on magnetic fields. These two cases, individually
or combined, will reduce and sometimes impede the tracing of the wire sections
affected.
Hint: Whenever possible the short circuit mode of operation should be used, be-
cause it provides with the best tracing capabilities.
13 - Special Tracing procedures
•
In all cases, first set the FF300R at the lower sensitivity level and increase it as nec-
essary. Proceed as indicated in the sections of this User’s Manual applicable to your
situation.
• Always after locating a probable fault area, verify several points in the wires on both
sides (before and after) the suspected area. The signal should be present at only one
side of the fault (open or short). This procedure will help avoid confusing a signal loss
with the actual trouble point.
13.1 Wire bundles and conduits:
Special care should be given in the case of tracing a wire inside a bundle or conduit
when there is a split. In this case it may be possible to follow the wrong branch for a
short distance and still receive a positive audio/visual indication.
8 - Tracing Wires inside bundles and conduits
Fig. 9 - Simplified dome light circuit hook up for wire tracing
Careful attention should be paid to the beeping and flashing speed of the tracer unit
indicators, as these provide the necessary feedback to evaluate the proximity of the
wire being traced.
13.2 How to increase the pick up range when tracing wires
• When tracing or identifying wires connected to lightly loaded circuit (low currents), these
reduces the range of pick up significantly. A possible solution is after connecting the
FF300T - transmitter in series with the circuit to trace, is to replace the load (light
bulb, module, etc.) with a direct connection to ground. This allows the FF300T to inject
a more powerful signal easier to detect.
•
For the cases in which it is suspected the layout of the wires is the cause of a very dif-
ficult to pick up or weak signal, a dramatic increase of the range can be accomplished
by “spreading” the circuit.
Fig. 7 - Detection field when tracing short-circuits with the FF300
Because the probe may be picking up the signal from the other nearby branch (the one
with the wire actually being traced). To avoid following the wrong path, the branches
should be swept maintaining the probe outside the apex area between the split, as
shown in figure 8 below.