9-5 Aero (9600) L4-2.3L Turbo (B235) HO (2000)
Backup Lamp Switch: Diagnostic Aids
General
Suitable instruments for diagnosing faults in the car's electrical system are a diagnostic tool, a voltmeter and an ohmmeter.
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Use a diagnostic tool or voltmeter to measure voltages in a circuit.
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If the voltmeter is analogue, it should have an internal resistance of at least 20 M ohm/Volt.
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Use a diagnostic tool or ohmmeter to measure the resistance of a circuit.
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The ohmmeter must not be used for taking readings of components containing semiconductors, e.g. control modules and time-delay relays, etc.
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When measuring resistance, the voltage supply to the system being tested must be disconnected as the test instrument feeds a small current into the
circuit being tested.
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This will ensure that no current is already flowing through the circuit and that a correct reading will be obtained.
Checking the Voltage