The purpose of this test is to assess the controlled output of the alternator in relation to electrical load on the battery.
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):
In the waveform below, Channel A indicates a stable battery voltage with no spikes or ripples. Channel B indicates the current flowing into the system with even peaks.
Note: The periodic spikes evident can be attributed to induced spikes from the injection circuit and are of no concern.
Go to the drop-down menu bar at the lower left corner of the Waveform Library window and select, Alternator voltage.
Refer to vehicle technical data for specific test conditions and results.
In a typical example, there should be a minimum of 10 amps output from the alternator when the engine is running and the headlamps and heater blower are switched on max:
|2 x headlamps at 60 watts||120 watts|
|Heater blower max speed||120 watts|
|240 watts divided by 24 volts = 10 amps.|
The recommended regulated voltage varies slightly between motor manufacturers but 24-volt vehicles are typically between 26 and 28 volts. It is equally important that the system is neither under- or over-charging.
The current available from the alternator may vary depending on the style of the charging system, alternator installed, engine speed, battery load/state of charge and drive pulley arrangement.
PicoScope can reveal some alternator faults, such as a faulty diode, that cannot be detected by simply checking the output current or the regulated voltage. Please refer to our Guided Test Alternator AC ripple/diode test for this additional test procedure.
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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