First of all check the wire whether it is conducting electricity or any damage that means any breakdown is there inside the wire it can't pass the electricity to check it is passing electricity or not we can use digital multimeter.
The first order of troubleshooting electrical problems is to check the presence of voltage at the load point in the circuit. Using a test light is a quick way to check for voltage, but a voltmeter is more accurate. Every electrical device also requires a certain amount of voltage to operate. A light bulb will glow with reduced brilliance as the voltage drops. Checking the load point for full battery voltage will tell you whether or not sufficient voltage is getting through. Sometimes undersized wiring can cause low voltage it is not something you will find in much original equipment wiring circuit. A final note regarding repairing electrical faults is that splicing wires do not just twist them together and wrap electrical tape around the connection. Use a solderless crimp-on connector or twist the wires together use shrink wrap electrical insulation tubing to seal the repair.
Some tips on how to diagnose electrical faults in your car include checking the power cord, the phone battery, or the driver's-side window washer. Additionally, check for shorted out wires and check the temperature of the engine oil.
Dimming lights indicate charging malfunctions and low system voltage. The culprit could be a dying battery, loose wires, or a malfunctioning alternator belt. If the check engine light of your dashboard lights it means that there is a minor or major issue with your car that needs auto electric repair.