The purpose of this test is to evaluate the integrity of the alternator phase windings and the performance of the diodes in the rectifier pack.
Connection for diagnostic work will vary dependent on application.
Technicians should whenever possible gain access to the test circuit without damage to seals and insulation. If this is not possible then make sure appropriate repairs are completed.
General connection advice.
PicoScope offers a range of options within the test kits.
Dependent on difficulty of access, choose from:
Testing sensors and actuators (to include relevant circuit/connectors):
Refer to the vehicle’s technical data for specific test conditions and results.
Typical values with engine idling:
The example waveform illustrates the rectified output from the alternator.
This waveform shows that:
The waveform above demonstrates a typical example of either a failed alternator phase winding or rectifier diode pack. (Either fault will produce near identical waveform)
The noise level obtained at point 1 (across the vehicle battery) may hinder diagnosis given the influence of other operational circuits whilst the engine is running. Moving your blue test lead from the battery positive terminal to the alternator main battery terminal (point 2) will help minimize this noise and reveal a more concise waveform.
You can read more about alternators in our Online training section under Technical information – The alternator.
This help topic is subject to changes without notification. The information within is carefully checked and considered to be correct. This information is an example of our investigations and findings and is not a definitive procedure. Pico Technology accepts no responsibility for inaccuracies. Each vehicle may be different and require unique test settings.
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