What Is Acc In Car Fuse Box

Okay, let's dive into the world of car fuse boxes and specifically, the enigmatic "ACC" fuse. Understanding this part of your vehicle's electrical system can be invaluable for anything from basic repairs to more advanced modifications. Think of this as your guide to unlocking one of the secrets hidden within your car's wiring harness.

Why You Should Care About Your Car's Fuse Box Diagram

Fuse box diagrams are the roadmaps of your car's electrical system. Knowing how to read and interpret them allows you to:

Diagnose Electrical Problems: Identify a blown fuse linked to a specific component (e.g., radio, cigarette lighter) and replace it.
Perform Basic Repairs: Troubleshoot issues by tracing circuits and understanding power flow.
Add Aftermarket Accessories: Tap into appropriate circuits for powering new components like dash cams, auxiliary lights, or aftermarket sound systems safely.
Understand Your Car's Electrical System: Gain a deeper understanding of how different parts of your car work together.

Key Specs and Main Parts of a Typical Fuse Box Diagram

A fuse box diagram typically consists of a graphical representation of the fuse box itself, along with a legend. Here's a breakdown:

Fuse Layout: Shows the physical location of each fuse and relay within the fuse box.
Fuse Rating (Amperage): Indicates the maximum current (measured in Amperes, often abbreviated as "A") that a fuse can handle before blowing. Common ratings include 5A, 7.5A, 10A, 15A, 20A, 25A, 30A, and higher. This is crucial for safety; always replace a blown fuse with one of the same amperage rating unless a service manual explicitly suggests otherwise.
Circuit Designation: Describes the component or system protected by each fuse (e.g., "Radio," "Power Windows," "ACC"). This is the key to troubleshooting!
Relays: Electromagnetic switches that control high-current circuits using a low-current signal. The diagram will show which relays control which systems (e.g., starter relay, fuel pump relay).
Connector Locations: May identify the location of various electrical connectors associated with the fuse box and the circuits it controls.

Decoding the Symbols: Lines, Colors, and Icons

Fuse box diagrams use a standardized set of symbols and conventions to represent electrical components and connections.

Lines: Represent wires or electrical conductors. Thicker lines typically indicate wires carrying higher currents.
Colors: Wire colors are often indicated on the diagram (e.g., "Red," "Blue/White"). This helps you trace wires within the wiring harness. Following the proper wire color, especially when splicing wires, is critical.
Icons: Standard symbols are used to represent various electrical components:
- Fuse: A simple rectangle, often with a number indicating its amperage rating.
- Relay: A box with a coil symbol inside, and lines representing the switch contacts.
- Ground: A symbol resembling a downward-pointing arrow or a series of stacked horizontal lines. Indicates a connection to the vehicle's chassis, which serves as the return path for the electrical circuit.
- Battery: A symbol with long and short parallel lines representing the positive and negative terminals, respectively.

Understanding the "ACC" Circuit

The "ACC" designation, short for Accessory, indicates a circuit that is powered only when the ignition key is in the "ACC" or "ON" position. It's not powered when the ignition is completely off. This is by design to prevent draining the battery when the engine is not running.

How It Works: The ACC Circuit in Action

The ACC circuit is usually powered directly from the ignition switch. When you turn the key to the "ACC" or "ON" position, the ignition switch connects the battery to the ACC fuse. This allows power to flow through the fuse and to the components connected to the ACC circuit. Common components powered by the ACC circuit include the radio, cigarette lighter (now often a 12V power outlet), and certain accessories.

Think of it this way: the ignition switch acts as a gatekeeper. It only allows electricity to flow to the ACC circuit when you've given it permission by turning the key.

Real-World Use: Basic Troubleshooting Tips for the ACC Circuit

Let's say your radio suddenly stops working. Here's how you can use the fuse box diagram to troubleshoot the issue:

Consult the Diagram: Locate the fuse box diagram (usually found in your owner's manual or online).
Identify the ACC Fuse: Find the fuse labeled "Radio" or "ACC" in the diagram.
Check the Fuse: Physically inspect the fuse. A blown fuse will have a broken filament. You can often see this through the clear plastic housing of the fuse.
Replace the Fuse: If the fuse is blown, replace it with a new fuse of the same amperage rating.
Test: Turn the ignition key to the "ACC" or "ON" position and see if the radio now works.
If It Blows Again: If the new fuse blows immediately or shortly after, there's likely a short circuit in the radio's wiring or the radio itself. This requires further investigation or professional repair.

Important Note: Always disconnect the negative terminal of the battery before working on any electrical components in your car. This prevents accidental shorts and potential damage to the electrical system.

Safety First: Risky Components and Precautions

Working with your car's electrical system can be dangerous if you're not careful. Here are some key safety considerations:

Battery: The battery can deliver a large amount of current, which can cause severe burns or even death. Always disconnect the negative terminal before working on any electrical components.
Short Circuits: Short circuits can cause fires and damage to your car's electrical system. Avoid creating short circuits by carefully inspecting wiring and connections before applying power.
Incorrect Fuse Ratings: Never replace a fuse with one of a higher amperage rating. This can overload the circuit and cause a fire. Using a lower rated fuse may cause nuisance blowing, but is generally safer than a higher rated fuse.
Airbags: Airbag circuits are highly sensitive and can be accidentally triggered. If you are working near airbag components, disconnect the battery and wait at least 30 minutes to allow the airbag system to discharge before proceeding. Refer to your vehicle's service manual for specific instructions.

Disclaimer: This guide provides general information only. Always consult your vehicle's service manual for specific instructions and warnings. If you are not comfortable working on your car's electrical system, seek the help of a qualified mechanic.

We have a sample fuse box diagram file available for download to further illustrate the concepts discussed in this article. Feel free to download it and use it as a reference when working on your car's electrical system. It includes detailed labeling of components and circuits, and color-coding to facilitate easy understanding of wire connections.