First check the belt drive's and the electrical connections' condition and functions.
Then check the power supply of the alternator. For this purpose, connect a suitable measuring device to alternator terminal B+ and the housing ground on the alternator. The measurement result must be equal to the battery voltage. The setpoint value in this case is the battery voltage with a maximum deviation of < 0.5 volts. If the voltage difference is greater, check the wiring for weak points, such as interruptions or contact resistance.
Checking the alternator charging voltage and charging current
Use a suitable measuring device and proceed as follows to measure the alternator output:
- Connect the current clamp as closely as possible to alternator connection B+
- Connect the red terminal (+) of the voltmeter to alternator terminal B+ and the black terminal (-) of the voltmeter to alternator ground
- Start the engine and let it idle.
- Then load the vehicle electrical system with approx. 40 amperes by switching on some electrical consumers. This can be achieved, for example, by switching on the low beam, interior blower, air-conditioning system and heated rear window
- Increase the engine speed to approx. 2000-2500 rpm and read the measurement results
In this process, the control voltage must not drop below the setpoint value (13.7 to 15.0 volts) by more than 0.5 volts and the amperage must be higher than the total current consumption of all activated consumers.