Diagnosing problems with vehicle lighting or electricals is not usually an easy process. Sometimes you can get something back up and running by banging on it a few times. This is especially true if you have a loose component that needs a bit of shaking to fix it. Other times, it’s not always that simple.
Unlike the ’60s and ’70s, vehicles today have just about everything electronically regulated and controlled. This means that in addition to the radio, vehicle lighting, and fans, there are more parts that need an electrical connection to run, but the good news is that your car’s electricals are designed to last a very long time without any problems. If your car has electrical problems, this article reviews the basics for diagnosing them.
Understanding Your Vehicle Lighting and Electrical
How Vehicle Lighting and Electrical Circuits Work in a Car
Most of the components in your car have a basic and simple electrical circuit.
You have a battery with a positive and negative terminal that wires are connected to. The wire on the positive side is first connected to a fuse before it reaches the electrical component. The wire on the negative side is connected to a switch before it gets to the other terminal of the electrical component.
The vehicle lighting, clock, and radio need power and an electrical ground to work. The power side is connected to the positive terminal (red wire) and the ground side is connected to the negative terminal (black wire). These are mostly showcased in the circuit using a red wire and black wire respectively. For a car component to work, you’ll almost always need to turn on a switch.
If by any chance something breaks down and stops working, here’s how you can go about diagnosing electrical problems in your car.
Basic Steps for Diagnosing Electrical Problems in Your Car
General steps for diagnosing electrical parts
- Start at the Fuse Box
Your car electrical problems could be caused by a bad fuse. A way to diagnose electrical problems in cars is to test the fuse with a test light.
Most cars will have more than one fuse box. The one found under the hood holds the larger fuses for components, such as electric fans and the alternator. The one found under the dash carries smaller fuses for parts, such as the clock and brake lights.
You can always check your owner’s manual or the underside of the fuse box cover to find a specific fuse for testing. Unplug the fuse and inspect it visually. Check for burn marks that could indicate it’s blown.
Test the fuse with a test light. With the test light connected to the negative battery terminal, take the tip of the light and put it on the contacts found on top of the fuses. You’ll need a working test light for this. If the fuse is fine, the test light should light up when you test the contacts. If it’s not, there could be something in the circuit that caused it to blow.
This is because fuses don’t normally blow up on their own. The connection between the fuse and the car component could be contacting the ground or the electrical component could be drawing too much current from the circuit. Both situations will cause the fuse to blow.
- Test the Wiring
All electrical circuits need wires to send power from the battery to the device being powered and back to the battery. If any of the wires delivering or returning power are not in good condition, they could be causing your car’s electrical problems. Diagnosing electrical problems caused by a broken circuit will need some patience.
To check for a wiring issue, start by connecting a test light to the negative battery terminal. Test the power side of the circuit by placing the tip of the test light where the wire connects to the vehicle component. If the light comes on, the wiring is good all the way from where it connects to the battery through the fuse box.
You’ll also need to test the ground side of the circuit. Simply connect the test light to the positive battery terminal and test the ground wire where it connects to the vehicle component. Remember to turn on the switch to close the circuit.
If the test light doesn’t light up, there’s something wrong along the circuit that needs to be checked. Wires can get hot after prolonged use and cause a particular connection to melt. Those located on the outside of the cabin also tend to get dirty and rusty, effectively stopping electricity from flowing.
- Test the Switch
Your car electrical problems could also be caused by a bad switch. There’s a chance you may have flagged it when checking the wiring connection on the ground circuit. This is especially true if the test light did not light up when you turned on the switch. You’ll need to pay closer attention to the switch when diagnosing electrical problems in your car.
You can start by checking if the switch is receiving ground from the battery. Simply place the tip of your test light onto where the ground connection meets the switch. The test light should light up if the connection from the battery is fine.
Next, you’ll need to check if there’s ground leaving the switch when you turn it on. If the test light doesn’t light up, you may have a bad switch. You can alternatively disconnect the switch and jump the wires to close the circuit. If the vehicle component works when you do this, you’ll have confirmed that you indeed have a bad switch that needs to be replaced.
What Should I Do If My Car Has Electrical Problems?
Diagnosing electrical problems in cars can seem like a daunting task—especially if you have little to no knowledge of how things work. We hope this guide helps you to locate the problem in your car. If you find your car does have electrical problems, remember to have them fixed professionally to avoid more problems in the future.
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