(Automatic Test Of Alternator Function)
Click on the symbol for vehicle communication to access the test.
All necessary instructions are found in the test and must be followed so that the test can evaluate the alternator function.
If component replacement is required, the test shall be repeated afterward to verify the repair.
Other information:
- Charge regulator
- Alternator
- 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.
Click on the symbol for vehicle communication to access the automatic test.
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.
| Battery temperature (T) °C) | Voltage (U), lower limit (V) | Voltage (U), upper limit (V) |
|---|---|---|
| +60 °C, +70 °C, +80 °C, +90 °C | 12.80 V | 13.60 V |
| +50 °C | 12.95 V | 13.75 V |
| +40 °C | 13.27 V | 14.07 V |
| +30 °C | 13.58 V | 14.38 V |
| +20 °C | 13.89 V | 14.69 V |
| -30 °C, -20 °C, -10 °C, 0 °C, +10 °C | 14.20 V | 15.00 V |
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.
Was a fault detected?
Yes - Refer to REPLACING CHARGE REGULATOR
No - Troubleshooting has been completed