General Technologies FF300 Fault Finder for Electrical Wiring Open / Short Circuit - Manual (Page 7)

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This is achieved by means of connecting a jumper wire between the live wire (preferably
at a termination point in the circuit such as a light bulb socket or a switch, etc.), and a
ground point somewhere else in the vehicle ( see Fig. 9). This last metod should be
used only as “last resource” and with the FF300R set to low sensitivity, as it may make
the pinpoint of the precise location more difficult due to the much increased range.
•
Always verify that the FF300T is connected in series with the circuit being tested and
that its red indicator light is on, as this confirms a proper connection and will limit the
amount of current flowing in the circuit.
13.3 Circuits with multiple loads or branches
When tracing circuits connected to, or which are powering multiple loads and/or
branches (See Fig. 10), and when these circuits are active or live, the bulk of the cur-
rent injected into the circuit by the FF300T will be directed to the short circuited branch
of the circuit. However smaller amounts of current (or stray currents) will flow to the
other branches as long as these provide a path to ground (i.e. close the circuit).
14 - Technical specifications
FF300T Transmitter
Voltage range: 6 to 36 Volts.
Indicator: Green LED indicator for Power On or Open Circuits.
Red Led LED indicator for short circuits.
Power source: 9-volt alkaline battery. Duracell MN1604 or equivalent.
Connector: Two 5 Amp. universal micro-clips with auto polarity
and 18” long cable.
Battery life: approx. 50 hours of use.
FF300R Tracer
Tracer Sensitivity: 3 User selectable levels (Low, Medium and High)
Tracer probe: Flexible 9” gooseneck insulated steel probe.
Indicator: Green LED indicator for Power On and Open Circuits.
Red LED indicator for short circuits.
Audio signal for shorts and opens.
Variable flashing and modulated audible signal.
Power source: 9-volt alkaline battery. Duracell MN1604 or equivalent.
Battery life: Approx. 50 hours of use.
Fig. 10 - Schematic of a single circuit with multiples loads
These stray currents present in the non-shorted branches of the circuit, and depending
on the circuit configuration and physical layout of the wires, could be picked up by
the FF300R (receiver), making the tracing procedures confusing, and even mis-
leading.
The simplest and most effective way to deal with these cases, is to disconect or re-
move all the loads from the circuit being traced (i.e. remove the light bulbs in example
shown above).