Automotive fuses are a class of fuses which are used to protect the wiring and electrical equipment for vehicles. They are rated for circuits no higher than 32 volts direct current, but some types are rated for 42-volt electrical systems. They are used occasionally in non-automotive electrical products.
How Fuses Work
This is a Step by step guide on how automotive fuses work, this information pertains to all vehicles.
A fuse helps to protect a circuit from overloading in extreme operating conditions or in the event of a short circuit. Most fuses are found in the vehicle’s power distribution center.
Inside the PDC are many heavy as well as light duty fuses which protect various circuits which demand a specific amperage.
All fuses are designed with an element which will melt in case the circuit amperage exceeds the fuse rating.
A fuse is usually defined by the amperage rating it’s designed to protect, such as this 30 amp fuse.
Fuse power is supplied through the positive battery cable which is attached to the positive side of the battery.
For removing a fuse for inspection, a tool is used which is usually supplied in the PDC.
Symptoms of a Bad or Failing Fuse
When fuses blow or have any issues, they can lead to problems with functions and accessories of the vehicle. Generally, a bad or blown fuse will produce a few symptoms that can alert the driver of a potential issue.
1. Accessories or functions lose power
One of the first symptoms of an issue with a fuse will be loss of power to one or more of the vehicle’s functions or accessories. Fuses are installed in line of specific circuits for protecting those circuits from potentially overloading. If those circuits do become overloaded, for any reason, the fuse will blow and cut off power to the circuit for protecting it from the possibility of damage. If you find that any of the vehicle’s functions or accessories, such as the radio, wipers, power windows or locks, etc, suddenly cease to function it might be related to a fuse.
2. Fuse is blown
Another, more direct symptom of a bad fuse will be a blown fuse. If the fuse is bad, upon retrieval and inspection the wire inside of the fuse will be broken, burnt, or otherwise disconnected. A blown fuse has to be replaced with a new one in order to restore function to the circuit. A blown fuse also needs to be investigated to determine what caused the fuse to blow in the first place.
While most fuses should last a long time as long as the vehicle’s electrical system is operating correctly, over time electrical systems and components can develop issues that lead the fuses to blow.
How to Inspect Car Fuses
A fuse box is found in the car and houses the fuses. Some cars consist of multiple fuse boxes with many different fuses. If something electrical in your vehicle suddenly stops working, start by inspecting the fuse box and get a certified mechanic to take a look and diagnose any electrical problems.
A) Locate the fuse box
- Needle nose pliers or fuse puller
- Test light
Most cars have more than one fuse box – some vehicles might even have three or four. Car manufacturers tend to install fuse boxes in different locations which will depend on the make of the car. It is best to refer to your owner’s manual to find the fuse box you need and also to determine which fuse controls each circuit.
B) Visually inspect fuses
Most fuse boxes will have a diagram which displays the name and location of each fuse.
Step 1- Remove the fuse.
With the car completely off, find the fuse in question and remove it by grabbing it firmly with the fuse puller stored in the fuse box, or with a pair of needle nose pliers.
Step 2- Inspect the fuse.
Hold the fuse up to the light and inspect the metal wire for signs of damage or a break. If you see either of these, you will be needing to replace the fuse.
C) Use a test light
If you do not have a fuse diagram to find a specific fuse, you can test each fuse individually with a test light.
Step 1- Switch on the ignition
Turn the key to position two on the ignition, also called Key On Engine Off (KOEO).
Step 2- Inspect the fuse with the test light.
Attach the clip for the test light to any of the bare metal, and use the probe of the test light to touch each end of a fuse. If the fuse is good, the test light will illuminate on both sides of the fuse. If the fuse is bad, only one side of the two sides will illuminate the test light.
- Tip: Utilize a computer-safe test light, preferably one with an LED light, as probing unknown fuses with an older style test light may draw excessive current. If you test a fuse for the airbag, it might deploy – so be careful!
D) Replacing the fuse
Once the damaged fuse is detected, ensure to replace it with a fuse of the same type and amp rating.
How to Change a Car Fuse
Step 1- Locate your car’s fuse panel.
You might need to check the owner’s manual, but they can generally be found under the steering wheel.
Step 2- Take off the fuse panel’s cover.
Inside the fuse box, you’ll see a range of colours as well as numbers that denote different amperages while a diagram (usually on the reverse of the cover) will show what each fuse powers in your car.
Step 3- Locate the blown fuse.
The inside will generally be black or the metal filament might be broken. If it’s dark, you might want a flashlight for making this a quicker job.
Step 4. Remove the broken fuse
For extracting the blown fuse, the important point is to fuse. You can make use of a variety of tools (or skip the tools and use your hands to use care. Fuses can break easily and a broken fuse is a lot harder to get out as compared to a fully intact one.
Step 5- Insert a replacement fuse of the correct amperage
Make note of the fuse panel as well as your owner’s manual on this one. Using a fuse of the incorrect amperage can lead to serious electrical problems.
Step 6- Keep a few extra fuses of different amperages in your glove box.
In a jam, you can always take a fuse away from a lesser used function of the same amperage and utilize it for something more pressing, but this is just a temporary fix. For instance, if the fuse for your power windows is blown and there’s no rain in the forecast pull the working fuse that’s allocated for your rear windshield wiper and use it for power windows. Ensure to double check that the amperages for each are the same.
Step 7- Start the ignition.
Check if your work has paid off or not.