Why Cars Have Fuses: What a Fuse Does & How They Work • Cars Simplified

Summary

This video script explains the importance of fuses in automotive electrical systems. It covers the basics of how fuses work, their role in protecting circuits, and the correct way to replace them. The script uses a simple circuit with a 12-volt battery, fuse, and headlight bulb to illustrate concepts. It warns against using fuses with higher amperage ratings than recommended, as this can lead to other components failing. The video also discusses the ideal placement of fuses for safety and efficiency, emphasizing the need to address the underlying cause of a blown fuse rather than just replacing it.

Takeaways

• 🔌 **Fuse as a starting point**: Always check the fuse first when dealing with car electrical issues.
• 💡 **Basic circuit components**: A typical car electrical circuit consists of a battery, a fuse, and a load (e.g., a headlight bulb).
• 🔗 **Circuit path**: The circuit's positive wire goes through the fuse to the load and returns to the negative post.
• ⚖️ **Resistance and amperage**: Components have a resistance rating in ohms, and the circuit's amperage can be calculated.
• 🚫 **Fuse rating**: Fuses are rated for a maximum amperage they can handle, protecting the circuit from overload.
• 🔄 **Consequences of incorrect bulb**: Using a bulb with lower resistance than specified can double the amperage, causing the fuse to blow.
• 🚫 **Avoid overrating fuses**: Replacing a blown fuse with one of a higher amperage is dangerous and can lead to other component failures.
• 🔩 **Component compatibility**: Circuit components are designed to work together within specified amperage limits.
• 🚗 **Fuse location**: The fuse is strategically placed near the battery to minimize the risk of short circuits and damage.
• 🔧 **Fuse replacement**: When a fuse blows, it's important to identify and fix the underlying issue before replacing the fuse.
• 👍 **Educational value**: The video aims to educate viewers on the importance of fuses and safe electrical practices in cars.

Q & A

Why is checking the fuse a common first step when dealing with electrical issues in a car?

Checking the fuse is a common first step because it's a simple and effective way to identify issues in the automotive electrical system. Fuses are designed to protect the circuit by breaking the flow of electricity when it exceeds a safe level, preventing damage to other components.

What is the primary function of a fuse in a car's electrical system?

The primary function of a fuse is to protect the electrical circuit by melting and breaking the circuit when the current exceeds its rating, thus preventing potential damage to the circuit and its components.

Where is the fuse typically located in a car's electrical circuit?

In the script, it is mentioned that the fuse is located between the battery's positive post and the load, such as a headlight bulb. It is placed as close as possible to the positive post to minimize the length of the unprotected circuit.

Why is it not advisable to replace a blown fuse with one of a higher amperage rating?

Replacing a blown fuse with a higher amperage one is not advisable because it can bypass the protection intended by the original fuse rating. This could lead to other components in the circuit, which are not designed to handle higher amperage, to overheat and potentially cause damage or even a fire.

What happens when resistance in a circuit decreases?

When resistance decreases, the amperage (current) in the circuit increases. This is due to Ohm's Law, which states that current (I) is equal to voltage (V) divided by resistance (R), or I = V/R. So if resistance (R) decreases, current (I) increases.

Why are fuses rated for specific amperages?

Fuses are rated for specific amperages to ensure they provide the correct level of protection for the circuit. The rating indicates the maximum current the fuse can handle before it blows, protecting the circuit from overloading and potential damage.

How does the location of a fuse in a circuit affect its function?

The location of a fuse in a circuit is crucial for its function. It should be placed as close to the positive post of the battery as possible to minimize the length of the unprotected circuit, reducing the risk of damage in case of a short circuit.

What is the role of the car's body in the electrical circuit as described in the script?

The car's body acts as a ground or negative terminal in the electrical circuit. It is connected to the negative post of the battery. If a wire breaks and touches the body, it can create a short circuit, leading to a dramatic increase in amperage and potential damage.

Why is it important to replace a fuse with the same amperage rating after it has blown?

It is important to replace a blown fuse with one of the same amperage rating to maintain the intended protection level for the circuit. Using a fuse with a different rating could either provide insufficient protection or allow too much current to flow, potentially damaging other components.

What should one do if they discover a blown fuse in their car?

If a blown fuse is discovered, one should first ensure that the circuit is safe to work on. Then, they should replace the fuse with one of the same amperage rating. It's also important to diagnose the cause of the blown fuse to prevent it from happening again.

Why is it critical to fix the cause of a blown fuse rather than just replacing it?

Fixing the cause of a blown fuse is critical because simply replacing it without addressing the underlying issue can lead to the new fuse blowing again. Identifying and fixing the cause ensures the electrical system operates safely and efficiently.

Outlines

00:00

🔌 Understanding Car Fuses

This paragraph explains the fundamental role of fuses in automotive electrical systems. It begins by emphasizing the importance of checking the fuse when encountering electrical issues. The script then uses a simple circuit diagram involving a 12-volt battery, a fuse, and a headlight bulb with a 1-ohm resistance to illustrate how fuses work. It explains that the fuse is rated for 20 amps, and if a bulb with half the resistance is installed, the amperage doubles to 24 amps, causing the fuse to blow. The paragraph cautions against replacing a blown fuse with one of a higher amperage, as this could lead to other components in the circuit overheating or burning out. It concludes by discussing the placement of fuses in relation to the car's body, which acts as a ground, to prevent short circuits and protect the circuit.

05:05

🛠️ Troubleshooting Blown Fuses

The second paragraph advises viewers against simply replacing a blown fuse without investigating the cause of the issue. It stresses the importance of identifying and fixing the underlying problem that led to the fuse blowing, rather than just swapping it with a higher amperage fuse, which could result in further damage. The script encourages viewers to engage with the content by liking the video if they found it helpful or by commenting if they believe important details were omitted. It ends with a note of appreciation for watching and a teaser for the next installment in the Cars Simplified video series.

Keywords

💡Fuse

A fuse is a safety device that protects an electrical circuit from damage caused by overcurrent. It is designed to blow or 'blow out' when the current exceeds a certain threshold, thereby interrupting the flow of electricity. In the context of the video, fuses are crucial for preventing damage to the car's electrical system. The video explains that if a bulb with lower resistance is used, it can cause the current to double, leading to the fuse blowing to protect the circuit.

💡Electrical Issue

An electrical issue refers to any malfunction or problem within an electrical system. In cars, this could range from a blown fuse to a faulty wiring. The video script uses the term to set the scene for discussing the importance of fuses as a starting point for troubleshooting car electrical problems.

💡Automotive Electrical Knowledge

This term refers to the understanding of how electrical systems function within vehicles. The video suggests that regardless of one's level of expertise in automotive electrical systems, checking the fuse is always a good first step when diagnosing issues.

💡Load

In electrical terms, a load refers to an electrical device or component that uses or consumes electrical power. In the video, the load is exemplified by a headlight bulb, which draws power from the car's electrical system.

💡Resistance

Resistance is a property of materials that opposes the flow of electric current and is measured in ohms. The video uses the concept of resistance to explain how changing the bulb's resistance (to half of its original value) can double the amperage in the circuit, potentially leading to a blown fuse.

💡Amperage

Amperage, measured in amperes (amps), is the rate of flow of electric charge. The video script explains that if resistance decreases, amperage increases, which can cause a fuse to blow if it exceeds the fuse's rating.

💡Circuit

A circuit is a closed loop through which electric current flows. The video describes a simple circuit consisting of a battery, a fuse, and a light bulb, emphasizing the role of the fuse in protecting the circuit.

💡Short Circuit

A short circuit occurs when the current takes an unintended path, bypassing the load and creating a low-resistance path to ground. The video warns that if a wire breaks and touches the car body, it can cause a short circuit, leading to a dramatic increase in amperage and potential damage.

💡Ohm

The ohm is the SI unit of electrical resistance. The video uses the term to describe the resistance rating of the components in the circuit, with the example of a 1-ohm headlight bulb.

💡Switch

A switch is a device that breaks or completes an electrical circuit, allowing control over the flow of electricity. Although not explicitly detailed in the script, the video mentions that a switch would typically be present in the circuit to control the light bulb.

💡Protective Device

A protective device is any component designed to prevent damage to an electrical system. The video highlights that fuses are protective devices that safeguard the circuit by blowing when the current exceeds their rating, thus protecting the wires, switches, and other components.

Highlights

Fuses are a crucial starting point for diagnosing electrical issues in cars.

A fuse's purpose is to protect the circuit from excessive current.

Understanding fuses involves knowing how they work and where they are located in a car.

A basic car electrical circuit consists of a battery, a fuse, and a load like a headlight bulb.

Components in a circuit have a resistance rating measured in ohms.

The circuit's amperage can be calculated using Ohm's Law.

A fuse is rated for a maximum current it can handle, such as 20 amps.

Using a bulb with lower resistance than designed can double the circuit's amperage.

A fuse will blow if the circuit's amperage exceeds its rating.

Replacing a blown fuse with one of higher amperage is not recommended as it can lead to further damage.

The fuse's role is to protect the entire circuit, not just prevent the use of non-standard bulbs.

Car components are designed to handle specific amperage levels for efficiency and cost.

If you change the circuit's amperage, you must upgrade all components in the path.

Fuses are placed close to the positive post of the battery for safety reasons.

The car's body acts as a ground or negative terminal.

A broken wire touching the car body can cause a short circuit and excessive heat.

The fuse's location minimizes the length of the unprotected circuit.

Blown fuses should not be replaced without identifying and fixing the cause of the issue.

Replacing a fuse with a higher amperage rating can lead to other components burning out.

Always use a fuse of the same amperage rating when replacing a blown fuse.

Transcripts

If you've had any sort of electrical issue on a  car before you've probably known, or have been  

told to check the fuse. No matter how advanced  your automotive electrical knowledge may be,  

the fuse is always a good place to start.  This video is going to explain why that is,  

why we have fuses in the first place, how they  work, where they go, and you may even learn some  

things about electricity along the way! So I'll  start by explaining what it is you're looking  

at we have a 12 volt battery that's common in  many cars we have a fuse and we have a load in  

this case the load is a headlight bulb the lines  I've drawn here are basically the wires you have  

a wire coming out of the positive post it goes  through the fuse to this light bulb and then  

it comes back to the negative post you have no  way of switching it on and off so you'd have a  

switch in there but I've left that out just to  keep this as simple as possible components that  

do stuff in your circuit tend to have a resistance  rating which is measured in ohms again to keep the  

circuit super simple for this example I've given  it a really easy number to work with which is 1  

ohm using math that we'll get into in a completely  different video this circuit is 12 amps so is this  

12 amp circuit going to blow this fuse well look  at the top of this fuse and we'll see that says 20  

a 420 amps so this fuse is rated to work up to  20 amps now let's say we put the wrong kind of  

bulb in this circuit this bulb is supposed to be a  1 ohm resistance bulb and we ended up putting in a  

point 5 resistance bulb when resistance goes down  amperage goes up in fact since the resistance is  

half of what it was before the amperage is going  to be double what it was before so he went from  

12 amps to 24 amps 24 is more amperage than this  20 amp fuse can handle so this fuse just blew and  

our circuit is incomplete now we don't get power  going through this area to the bulb and the bulb  

does not light up now with this understanding  of how many amps are flowing through the circuit  

you may be tempted to go ok I get it this 20 amp  fuse is not going to be able to handle that let's  

replace it with a 30 amp fuse you do not want to  do that this fuse is here to protect everything  

on the circuit not just prevent you from putting  your fancy headlight bulbs in when an engineer  

does and the circuit they did the math on what  this bulb is going to run amperage wise and they  

selected wire specifically for that circuit  if they designed all the components to handle  

way more amperage than they were ever going to  experience in normal situations the car would  

be a lot more heavy and a lot more expensive but  this 20 amp view is selected they probably picked  

a wire that can flow 21 or 22 amps same goes for  the switch or relay that they selected for that  

circuit and same with the socket that this bulb  plugs into if you want to change this part out  

and make the circuit a different amperage you're  gonna have to upgrade everything along the path  

if you accidentally started running 24 amps on the  circuit like we were describing earlier this fuse  

would blow out if you were to use a 30-amp fuse  instead something else on this circuit is going  

to burn up instead when it comes to replacing  parts in a circuit typically the fuse is both  

the easiest to get to and the least expensive now  let's get into why the fuse is located where it  

is let's switch these components around in a  series circuit like this one amperage is the  

same the entire path amperage does not blow out  components in the order that it reaches them so  

technically this layout would work however we  are going to keep the fuse here for a reason on  

pretty much every car the entire body is a ground  or let's call it negative for simplicity sake so  

it's connected to the negative on this battery if  this wire breaks and then suddenly falls down and  

touches the body you have a short there's nothing  from positive to negative that's going to consume  

that power so amperage spikes up dramatically  because there's pretty much no resistance on  

the circuit that amperage is going to create a lot  of heat and that heat is going to affect the weak  

points of the circuit first and that weak point  on this particular layout is in the center of  

this fuse so we're going to pull this fuse out  before we put a new fuse in we have to fix this  

wire we've spliced in a new wire and now we can  put in a new fuse and make sure it's always the  

same amperage so what would happen if that same  scenario that happened here happened here instead  

well the power flow through here and then you'd  have four wire meltdown and then you probably  

have to replace this section of wire and you might  have some body area that's melted and you have to  

fix that too but that's really unlikely because  this wire is coming off the battery and going to  

the fuse box the wire leading from the battery to  the fuse box shouldn't encounter a whole lot of  

movement or potential for damage so that scenario  is unlikely but it is possible still with that in  

mind the closer you can get your fuse to this  positive post the less unprotected circuit you  

end up with so for safety's sake let's relocate  this fuse right here from here to here is protect  

it now what it wasn't before so if you're working  on your car and discover that there's a blown fuse  

don't just pull it out and stick it going in and  definitely definitely do not try to replace that  

fuse with one with a higher amperage so you don't  blow it that fuse melted down so something else on  

the circuit didn't you or your mechanic are gonna  have to figure out what component was causing  

the issue and repair or replace it if you learn  something or enjoyed the way that I presented this  

give this video a like. If you feel like I missed  some important details let me know in the comments  

below. Either way, thanks for watching and  I'll see you in the next Cars Simplified video!