Some simple measurement methods
| Some simple measurement methods |
| Measuring equipment |
Suitable instruments for diagnosing faults in the car's electrical system are the diagnostics instrument, a voltmeter and an ohmmeter.
Use the diagnostics instrument of a voltmeter to measure the voltage in a circuit. If the voltmeter is of analogue type it should have an internal resistance of at least 20 Mohm/Volt.
Use the diagnostics instrument or an ohmmeter to check for short circuits and open circuits in wiring harnesses, connectors, switches and contacts. The ohmmeter must not be used for taking readings on components which contain semiconductors, such as relays with a time function and control modules. When measuring resistance, the car's battery must be disconnected as the instrument has a built-in battery which supplies current to the circuit being measured. This will ensure that no current is already flowing through the circuit and that a correct reading will be obtained.
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