Quick Test of Alternator Function
Quick test of alternator function
Quick test information
The central electronic module (CEM) has built-in functions for regulating the alternator (alternator control module (ACM)).
To charge the battery optimally, output voltage from the alternator is calculated based on the calculated battery temperature. The central electronic module (CEM) calculates battery temperature from outside temperature, which is obtained from the outside temperature sensor.
Depending on the vehicle's ambient temperature and/or if the vehicle has been without power, the calculated battery temperature (read temperature) may differ slightly from the battery's actual temperature for up to 24 hours afterwards.
In the following tests, battery temperature in the central electronic module (CEM) is changed, thereby changing voltage from the alternator.
The test is divided into two parts - an automatic test and a manual test.
Select one of the alternatives below:
1. Automatic test of alternator function.
2. Manual test of alternator function.
1 - Automatic test of alternator function
2 - Manual test of alternator function
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Automatic test of alternator function
- Start the engine and allow it to idle for approx. 1 minute.
- Make sure that no extra electrical consumers are connected. Turn off functions that consume a great deal of power, such as the ventilation fan, heated rear window/door mirrors, heated seats, lighting, radio system, etc.
Start the automatic test by clicking the Start button.
Values for battery temperature and voltage are read and displayed continually during the test. A number of tests are performed in which various battery temperatures are used from -30 °C to +90 °C. Between each battery temperature, there is a delay of approx. 5 seconds before the voltage is read. This allows the alternator to have time to set the right voltage in relation to the set battery temperature.
The entire test takes approx. 1 minute. A message is displayed when the test is complete. Compare the values from the readout of battery temperature (T) and voltage (U) with the values in the table.
If the voltage values generally lie below the lower limit (low voltage), redo the test at an engine speed of 2500 rpm.
If the voltage is within the tolerances this time, alternator function is OK, but the test indicates that the battery is not fully charged. If voltage still deviates, there is a fault in the charging system.
Note! The read-out voltage is read internally from the central electronic module (CEM) and deviates slightly from the actual alternator output voltage due to a drop in voltage in the wiring harness.
Continue - DONE
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Manual test of alternator function
- Start the engine and allow it to idle for approx. 1 minute.
- Make sure that no extra electrical consumers are connected. Turn off functions that consume a great deal of power, such as the ventilation fan, heated rear window/door mirrors, heated seats, lighting, radio system, etc.
Values for battery temperature and voltage are read and displayed continually during the test. Select values that are available in the list window. Wait approx. 5 seconds between each battery temperature change to allow the alternator to have time to set the right voltage in relation to the set battery temperature. Then read battery temperature and voltage between each temperature selection.
Compare the values from the readout of battery temperature and voltage with the values in the table.
If the voltage values generally lie below the lower limit (low voltage), redo the test at an engine speed of 2500 rpm.
If the voltage is within the tolerances this time, alternator function is OK, but the test indicates that the battery is not fully charged. If voltage still deviates, there is a fault in the charging system.
Note! The read-out voltage is read internally from the central electronic module (CEM) and deviates slightly from the actual alternator output voltage due to a drop in voltage in the wiring harness.
Continue - DONE
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