An electrical problem in a car stems from the nature of electrical circuits. An electrical device in a car must be part of an electrical circuit capable of providing the required voltage and current. If this is not the case, or if the device is defective, it will fail to operate as expected. There are three possible causes for an electrical problem.
When a light bulb burns out, a fuse "blows," or a circuit breaker "pops" (or is defective), the circuit loses its continuity and the devices on the circuit stop functioning. Loss of continuity also can be caused by a broken wire or a loose connector. This type of problem will affect one or a limited number of devices. A general problem that can affect the entire vehicle is no (or low) voltage for the circuits.
The car's battery supplies the current for the car's electrical circuits. There will not be enough current to properly operate the devices unless the battery is sufficiently charged. Insufficient charge can be caused by a defective battery, voltage regulator or alternator. Low voltage also can be caused by poor connections to the battery. Relays, and especially the starter solenoid, may not operate if the voltage supplied is too low. Other devices affected may be fuel injectors and your electronics, such as the radio and electronic control module.
High resistance through a loose or corroded battery cable, connector, ground contact or partially severed wire can reduce the available voltage at a device. Faulty switches or relays also can create high resistance problems. These can result in dim lights, or devices such as solenoids failing to operate at all. Aftermarket accessories, such as additional lights, may overload circuit wiring and cause low voltage at the devices.
Sometimes electrical problems are intermittent. They may be caused by loose or corroded connections, by the car heating up or cooling down, by vibration or moisture. These problems can be difficult to diagnose.
Replacing a battery or removing the negative cable for safety reasons during maintenance may cause an electronic control module to forget its learned settings. This is an "electrical problem" that is really an electronic problem. Read your owner's manual before disconnecting the negative cable on your automobile's battery.
