A guide to different types of automotive blade fuses.

Car fuses help to protect your vehicle in the event of unforeseen circumstances such as short circuits and over current conditions. They work simply as a disposable part which disconnects the power when these conditions occur. Many different types are available including standard ATO type blade fuses, mini blade fuses and the large maxi blade fuse designed for high current applications.

Most modern car fuses are blade type fuses utilising the same basic construction of two pins inside a coloured plastic body which is stamped with the current rating of the fuse. Their uses today are not just limited to vehicles, and are now commonly found in DC based circuits in solar power systems, solar regulators - even our own Redback pro audio amplifiers utilise a standard blade fuse!

How to check a blade fuse.

Blade fuses generally should not need replacement unless they have blown. A visual check through the body of the fuse is usually enough confirmation to see that the fuse has gone to fuse heaven. In situations where the fuse block is difficult to access you can confirm continuity of the circuit by using a multimeter or automotive voltage probe.

What fuse do I need?

It is important to choose the right fuse for the task to prevent additional issues and to ensure the correct operation of your vehicle or equipment. Always replace an existing fuse with one of the same value. If the fuse blows again, this means the condition that caused the fuse to blow has not been resolved. Never select a higher value just to prevent the fuse from blowing. Consult a professional if in any doubt, a trip to the auto electrician could save you from damaging your vehicle - or worse - losing it to a fire!

Car blade fuses are named by their size and amperage rating. Each has a colour which has been defined by an international standard. They are shown in the table below:

Fuse Sizes

There are size common types of automotive blade fuses. These are shown in the diagram below:

Standard Blade (ATO) Fuse: The most common type of fuse in use, found in majority of vehicles produced since the late 1980's.

Micro2 Blade Fuse: A mini version of the standard blade fuse with legs which protrude from the coloured plastic housing.

Mini Blade Fuse: A compact blade fuse design with prongs protruding below the plastic housing with triangulated (champhered) ends.

Low Profile Mini Blade Fuse: A short and stubby mini fuse with very short legs almost the same height as the plastic housing.

Maxi Blade Fuse: Hard to miss, this one is roughly three times the size of a standard blade fuse and offers currents up to 80A. These are commonly found in remote power battery boxes.

Why do fuses blow?

Fuses are designed to blow in order to protect from dangerous short circuit and over current conditions in equipment. A fuse blowing indicates that it has prevented a potential disaster by stopping excessive DC current from flowing through wiring and equipment. Typical reasons for a short circuit condition occurring would be equipment failure, physical damage to the wiring or incorrect connection of equipment by a user.

During a short circuit condition the current flow will rapidly rise within seconds, causing a condition that if allowed to continue will cause a complete failure of the wiring, connected equipment and even the battery.

This is why is it always essential that any DC circuitry in your vehicle (particularly aftermarket installations) are correctly installed with a DC fuse or breaker on each circuit.

How do I choose the right fuse for my circuit?

If you're simply replacing an existing fuse in a standard vehicle circuit then the choice is simple, just pick the same rating! But if you've added wiring for your spot lights, or a solar battery charging system, the choice is less obvious and is dependent on your chosen wiring and the appliance rating.

For more information on this process, see our companion article "How to choose the right fuse rating for your vehicle wiring"

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