Visual inspection
* Check for damage, cracks, loose or loose connections on wires, connectors, battery and starter.
* Look for any signs of corrosion, rust or varnish.
* Check that all components are connected correctly and there are no signs of overheating or melting.
Electrical measurements
Voltage:
* Measure the voltage on the battery. It should be between 12.6-13.2 volts (cold).
* Check the voltage at the generator. It should be between 13.8-14.2 volts with the engine running.
Current:
*Measure the current consumed by the car. This will help identify possible current leaks.
* Check generator current. It must be sufficient to power all electrical systems of the vehicle.
Resistance:
* Measure the resistance of the ground wires. It should be close to zero.
* Check the resistance of wiring and components. High resistance may indicate damage or a poor connection.
Power:
* Measure the power of the generator. It must be sufficient to meet all the electrical needs of the car.
Using a trouble code scanner (OBD-II)
* Connect the scanner to the car.
* Read fault codes related to electrical systems.
* Decipher and analyze the codes.
Testing specific components
* Starter: Check its condition using a starter tester or wire.
* Generator: Check its performance using a generator tester or a device with an ammeter function.
* Battery: Stress test or check battery capacity with a battery tester.
* Fuses and relays: check their functionality using a tester or by replacing them.
* Electric motors and electric drives: check their performance using a voltmeter or oscilloscope.
Additional steps:
*Check for wiring problems by performing a continuity test.
* Study a vehicle wiring diagram to better understand the electrical system.
*Consult a qualified auto mechanic if you are unable to accurately diagnose the problem.