Bussmann FMM-20 MAXI Fuse Instruction Manual

1. Introduction

This manual provides essential information for the proper use, installation, and maintenance of the Bussmann FMM-20 MAXI Fuse. The FMM-20 is a 20 Ampere (blue), micro female, slow-blow fuse designed for automotive applications, offering circuit protection in modern vehicles. Please read this manual thoroughly before installation or replacement to ensure safe and effective operation.

2. Product Overview

The Bussmann FMM-20 MAXI Fuse is engineered to meet the demands of high-current circuit protection in compact spaces. Its "slow-blow" characteristic allows it to withstand temporary current surges without blowing, while still providing protection against sustained overcurrent conditions.

Key Features:

• FMM Series: Female Micro Slow-Blow MAXI Fuse.
• 20 Amp Rating: Indicated by the blue color and "20" marking.
• Compact Design: Smaller size (0.59 inches tall) suitable for modern vehicle fuse boxes.
• Industry Standard: Color-coding adheres to industry standards for amp rating identification.
• Quality Assurance: UL recognized, meets or exceeds OEM and SAE standards.

Figure 1: A close-up view of the Bussmann FMM-20 MAXI Fuse, featuring its blue plastic body and a clear top indicating '20' for 20 Amperes. This fuse is designed for automotive electrical systems.

3. Specifications

4. Installation and Replacement

Fuses are critical safety devices designed to protect electrical circuits from overcurrent. Always ensure the vehicle's ignition is off and the battery is disconnected before attempting any fuse replacement.

Procedure:

1. Safety First: Turn off the vehicle's ignition and disconnect the negative terminal of the battery to prevent accidental electrical shorts.
2. Locate Fuse Box: Refer to your vehicle's owner's manual to locate the fuse box (typically under the hood, dashboard, or in the trunk).
3. Identify Blown Fuse: Use the fuse diagram in your vehicle's manual to identify the fuse corresponding to the faulty circuit. A blown fuse typically has a broken metal filament visible through its clear top.
4. Remove Old Fuse: Carefully use a fuse puller tool (often found in the fuse box lid) or small pliers to extract the blown fuse. Avoid using metal tools that could short circuits.
5. Insert New Fuse: Insert the Bussmann FMM-20 MAXI Fuse into the empty slot. Ensure it is firmly seated. Always replace a fuse with one of the exact same amperage rating and type (e.g., 20A FMM-20). Using a fuse with a higher rating can lead to severe electrical damage or fire.
6. Reconnect Battery: Reconnect the negative battery terminal and turn on the ignition to test the circuit.

If the new fuse blows immediately, there is an underlying electrical issue that needs to be diagnosed by a qualified technician.

5. Operation

The Bussmann FMM-20 is a "slow-blow" fuse. This means it is designed to tolerate temporary current spikes that are common during the startup of certain electrical components (like motors or compressors) without immediately breaking the circuit. However, if an overcurrent condition persists, the fuse will blow, interrupting the circuit and preventing damage to the wiring or connected components. The blue color signifies a 20 Ampere rating, which is a standard identification method in automotive electrical systems.

6. Maintenance

Fuses generally require no maintenance beyond replacement when they blow.

• Regular Inspection: Periodically check fuses in critical circuits if you suspect intermittent electrical issues. Visually inspect the filament through the clear top.
• Proper Storage: Store spare fuses in a dry, cool place, away from direct sunlight and extreme temperatures.
• Correct Rating: Always ensure that any replacement fuse matches the original fuse's amperage rating and type.

7. Troubleshooting

If an electrical component in your vehicle stops working, a blown fuse is a common cause.

• No Power to Component: If a light, radio, or other electrical device fails, check the corresponding fuse in the vehicle's fuse box.
• Fuse Blows Immediately After Replacement: This indicates a short circuit or an excessive current draw in the system. Do not continue to replace the fuse without addressing the underlying problem, as this can cause serious damage or fire. Seek professional automotive electrical diagnosis.
• Intermittent Issues: Sometimes, a fuse may have a hairline crack in its filament, leading to intermittent operation. A visual inspection might not reveal this; testing with a multimeter for continuity can confirm.

8. Safety Information

• Electrical Hazard: Always disconnect the vehicle's battery before working on electrical systems to avoid electric shock or short circuits.
• Correct Fuse Rating: Never use a fuse with a higher amperage rating than specified by the manufacturer. This can lead to overheating, wiring damage, and fire.
• Proper Tools: Use non-conductive fuse pullers or appropriate pliers for fuse removal and installation.
• Professional Help: If you are unsure about any electrical work or if fuses repeatedly blow, consult a qualified automotive technician.
• Proposition 65 Warning: This product may contain chemicals known to the State of California to cause cancer and birth defects or other reproductive harm. Wash hands after handling.

9. Warranty and Support

For specific warranty information regarding your Bussmann FMM-20 MAXI Fuse, please refer to the packaging or contact Bussmann customer support directly. General product support and technical assistance can often be found on the official Bussmann website.

Manufacturer: Bussmann