Every electrical component in your car requires a specific voltage level in order to work properly. If the voltage drops below the threshold level, the component will not work at all. Therefore, you can use voltage checks to troubleshoot problems with the electrical system in your vehicle. You need a voltmeter to conduct these voltage checks
Sometimes you car may refuse to start because there is insufficient voltage getting through the load point. You should connect the positive battery tester cable to the positive terminal on the battery and the same for the negative terminal. A battery that is seventy percent charged should give a voltage reading of about 12.43 Volts or more. If the voltage reading is much lower than this, it means you need to charge the battery and test it again. If your battery is working properly, you should get a voltmeter reading within 1 volt of battery voltage at different circuit load points in all the electrical circuits in your car.
If you find a low circuit voltage in any of the circuits in your car after testing using the voltmeter, it could also be due to excessive resistance in the wiring. The reasons for this resistance include corroded connectors, loose connectors or faulty switches. You need to find the point with the highest resistance in order to locate the problem. You can do this using the voltage drop technique. This involves checking the voltage at various points in the circuit and finding the difference in voltage. Any drop more than 0.4 volts across a connection means that that particular connection is faulty. Usually the voltage drop is 0.1 volts or less across a connection in the circuit.
Battery terminals and body ground straps
If you are unable to start the car completely and operate most of the electrical components, you should to the voltage drop test across a number of circuits, if there are voltage problems throughout this circuits then the battery cables are probably corroded or the ground straps are lose. You can repair this problem easily by cleaning and tightening the cables.
Some aftermarket accessories that you add to your vehicle may not have the same wiring design as the original equipment from the car manufacturer. Voltage problems arise when there is undersized wiring, which affects the performance of the electrical system of the car. You need to be very keen on following the recommended wire gauge sizes when installing after-market upgrades and replacements in your vehicle.
For more information, check out companies such as Drive-in Auto Electrics.