Al Thuraya Auto Services 1.95

Automotive Electrical Systems
Many automotive systems, such as the headlights, starter, safety features, electronic control unit, and sound system, run on electricity. In most cars, the metal body of the car itself forms part of the circuit, grounding the systems and connecting each component to the negative side of the battery. Without a functioning battery and electrical system, a car cannot start or function.

All electrical equipment and components in a car are powered by the battery, which also regulates system voltage. Car batteries are 12V, as automotive electrical systems run at 12V DC. The battery is charged by an alternator, which generates electricity by putting electromagnetic friction on the engine while it runs. The heart of an automotive electrical system is the fusebox or power center, the central point from which every electric circuit connects. Fuses protect each electrical circuit from damage, by burning or blowing out in case of overcurrent. Each piece of electrical equipment is connected to the fusebox and the battery by a system of wires and connections, generally going through relays, switches, and other components. Finding problems in these circuits, such as corroded connections, blown fuses, broken wires, faulty switches, or broken components, is the basic process of diagnosing automotive electrical problems.

Troubleshooting Common Electrical Problems
Electrical systems are complex, and some problems, like issues with the onboard computer, may need to be serviced at a repair shop or dealership. Many common issues, however, are fairly simple to diagnose and repair at home. With a few tools, most systems can be checked, and potential issues can be narrowed down to find the true problem.

Safety Information
Working with the electrical system in a vehicle is generally quite safe. Automotive electrical systems run at 12V, which does not pose a danger of shocks or electrocution. However, many electrical components are easily damaged, so care should be taken when handling them. Introducing incorrect voltages or currents can break many systems. One part of the electrical system that is potentially dangerous is the high-voltage side of the ignition coil, which should not be serviced while power is applied. Additionally, electric or hybrid-electric vehicles use many high-voltage batteries and powertrains, which are dangerous and potentially fatal if mishandled.

Tools Required
The simplest tool that can be used in electrical diagnosis is a 12V test light. This light can be used to check if power is being received at any point in a circuit, which can be handy for simple or quick tests. However, test lights do not provide very much information. A digital multimeter, or DMM, has two probes that can be connected to a circuit to test voltage, amperage, resistance, continuity, and more. With a DMM, most electrical problems can be diagnosed. Basic electrical and automotive tools, such as wire cutters, wrenches, and screwdrivers, are used to service automotive electrical systems.

Checking the Battery
Battery problems are the most common cause of electrical issues in vehicles. To test a battery, connect a multimeter in voltage mode across the terminals of the battery. A fully charged battery should read 12.6V, while a halfway-charged battery will be around 12.4V. A battery that shows 0V is dead and needs to be charged. One common problem is loose or corroded connections at the battery post, which can cause intermittent problems or prevent starting. Cleaning the posts and connections with a wire brush and tightening them will solve these problems.

A battery that frequently goes dead might simply be old, and can be tested at an auto-parts store. A good battery that still goes dead is an indication of an electrical problem. With the car off, disconnect the negative battery cable and connect the multimeter in amperage mode in between the negative battery post and the cable. A reading of more than 50mA indicates a parasitic load somewhere in the system that is draining the battery. Disconnect fuses one by one from the fusebox while checking the reading. When the system that is draining the battery is disconnected, the multimeter reading will drop to below 50mA.

Grounding Problems
Another common problem in automotive electrical systems is improper grounding connections. In a vehicle, the metal body of the car serves as a ground, and connects each component back to the negative post on the battery. Each component and system is connected to by a grounding connector, which is generally an O-ring connected to a screw post. Vibration from driving can cause these connections to become loose over time, which opens the circuit, causing failure or intermittent issues. Cleaning and tightening these connections solves most grounding issues.

Checking and Replacing Fuses
If a system, such as the radio or headlights, suddenly stops functioning, it is likely that a fuse has blown. Fuses are located at the fuse box, underneath the dash on the driver’s side, or in the power center under the hood. Each should have a diagram showing which fuse goes with which system. Fuses protect electrical systems and components by opening when too much current is flowing in the circuit. When a fuse blows, the wire connecting each side burns open, disconnecting the circuit. Replacing blown fuses with a new fuse of the same amperage rating reconnects the circuit. If a fuse has blown, it is likely that the problem is a short or overload in the circuit or component the fuse is protecting. If this is the case, replacing the fuse only fixes the problem temporarily.

Low Voltage
Dim headlights, slow starting, and other problems of degree are usually due to low voltage. Undervoltage occurs when a component is still receiving power, but not at the voltage it requires for proper operation. Undervoltage is usually caused by a connection, switch, or ground wire using, or dropping, more voltage than it should. Ideally, these circuit components should have zero resistance and thus drop no voltage, but in reality, each component drops a small amount. In proper condition, these voltage drops are small, and do not add up to a significant problem. However, corroded connections, undersized wires, worn-out switches, and other problems can quickly add up to an undervoltage situation. Test voltage drop by placing the probes of a multimeter on either side of a component.

The following table describes the maximum acceptable voltage drops for automotive electrical system components.

Component
Max. Acceptable Voltage Drop
Connection

0.00V

Wire or cable

0.20V

Switch or relay

0.3V

Ground connection

0.10V

If voltage drops exceed these levels, the component needs to be repaired or replaced. For connections and grounds, this is usually as simple as cleaning them with a wire brush and securing. Wires that drop voltage are usually worn out, corroded, or undersized for their application. Switches and relays that drop voltage generally need to be replaced.

Buying Automotive Electrical Tools and Supplies on eBay
One place online where you can find the tools and components needed for automotive electrical diagnosis is eBay. With thousands of items offered by sellers all over the world, finding the right supplies on eBay is easy. Furthermore, eBay sellers typically offer competitive prices and sometimes even free shipping.

A simple eBay search for “multimeter” or “12V test light” brings up listings for the basic testing tools needed. eBay Motors is also a great place to search for fuses, headlights, and other electrical equipment.

To get started on eBay, new users can simply register for a free account. To find any specific component, just enter a few keywords in the search bar from any page of the eBay website. Search listings can also be narrowed using filters for price, shipping cost, condition (new or used), buying format, and other parameters. When you are ready to check out, select PayPal as the payment method to guarantee a safe and easy transfer of funds.

Conclusion
Electrical systems power most of the equipment on a car that is not directly related to the drivetrain. Problems in the electrical system can range from relatively minor problems, like a radio that cuts out, to major safety concerns, such as non-functioning headlights. Automotive electrical problems can also prevent a car from starting.

Compared to residential systems found in homes, electrical systems in automobiles are fairly simple and safe to work with. Diagnosing most electrical problems only requires a few simple tools, such as a digital multimeter. Many common problems are caused by corroded connections, loose wiring, or other issues that are straightforward to fix. Finding faulty components, testing the battery, replacing fuses, and more can all be done by gearheads and beginners alike. Understanding basic electrical theory and how automotive electrical systems work is all that is required for basic diagnosis and repair.