Contact problems
Intermittent contact or temporary recurring faults can
be
difficult
to fault trace, and are frequently caused by
oxidation, vibration or poorly terminated cables.
Wear can also cause faults. For this reason, avoid dis-
connecting a connector unless it is necessary.
Other contact problems can be caused by damage to
pins, sockets and connectors etc.
Shake cables and pull connectors during measure-
ment, to find where the cable is damaged.
Contact resistance and oxidation
Resistance in connectors, cables and junctions should
be approx. 0 Ω. A certain amount of resistance will
occur, however, because of oxidation in connectors.
If this resistance is too great, malfunctions occur. The
amount of resistance that can be tolerated before mal-
functions occur varies, depending on the load in the
circuit.
Open circuit
Possible reasons for faults could be chafed or broken
cables, or connectors which have come undone.
Use the wiring schedule to check the cables which are
relevant to the function. Start off with the most probable
cable in the circuit.
Check the following:
•
Disconnect the relevant connector at each end of
the cable harness.
•
Use 88890074 Multimeter to measure the resist-
ance between the ends of the cable.
Nominal value ~ 0 Ω.
•
If possible, shake the cables and pull the connectors
during measurement to discover whether the cable
harness is damaged.
•
Check the next cable system in the wiring schedule
if no fault has been found.
30-2 Fault Tracing
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