How to Identify Car Fuses

Most cars use one of six blade fuses, and they're easy to mix up. Here's how to tell them apart in four quick checks, with every type drawn to scale, a size chart, the colour codes, and a true-size view you can hold your fuse against.

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How to identify a car fuse in 4 steps

Pull the fuse and check these in order. Most people know what they have by step 2.

1. Count the blades

Three flat blades means a Micro3. Two blades, keep going. No blades at all? A glass tube with metal caps is an AGU, and a flat fuse with bolt holes is an ANL or Mini ANL.

2. Measure the width

Measure the coloured body across. About 19 mm is an ATO/ATC, about 11 mm a Mini, about 9 mm a Micro2, and around 29 mm a Maxi. No ruler? A Canadian dime is 18 mm across.

3. Check the height

Mini width but squat, sitting almost flush in the fuse box? That's a low-profile Mini, about 9 mm tall. A regular Mini stands about 16 mm tall with its blades showing.

4. Read the number, then the colour

The amp rating is stamped on top. The colour confirms it on blade fuses, but Maxi fuses use a different colour code, so trust the number. Replace a fuse with the same type and rating.

Free tool

Identify your fuse

Tap a fuse to see its size, other names, colour code and the right fuse tap. Not sure? Answer a few questions, or hold your fuse against the screen in True size.

Blade fuses

Drawn to scale with each other

Amp and power wire fuses

Car audio and high-current runs
Enlarged

Sizes are nominal and from manufacturer specifications. Always replace a fuse with one of the same type and rating.

Troubleshooting

How to read a blown fuse

Before you fit a new fuse, look closely at the old one. The way the link broke usually tells you why it blew, and whether a new fuse will just blow again.

A blown Mini fuse with a broken link next to a good fuse with its link intact
Left: blown. The link inside has broken. Right: good. The link runs unbroken from blade to blade.
Good

Link intact

The fuse is fine. The problem is somewhere else on the circuit, so check the next fuse or the device itself.

Over current

A small, clean break

A neat gap in the link, with a clear, clean casing, generally means over current, not a short. The circuit drew more than the fuse is rated for, long enough to melt the link at its narrowest point. Fit a new fuse of the same rating. If that blows too, something on the circuit is drawing too much, like an add-on accessory or a failing motor.

Dead short

Burnt link, burn marks or debris

A link that's burnt away, with black burn marks or bits of metal on the inside of the casing, is a dead short: a wire or part touching ground. Short circuits are explosive, and it shows. Find and fix the short before you fit a new fuse, or it will blow the same way.

A clean break isn't always over current

An intermittent short, like a wire that only touches ground over bumps or when a door opens, can sometimes leave a clean break too. More often than not, though, a short circuit blows the link apart. If a new fuse blows straight away, or every time something moves, treat it as a short.

Check a fuse without pulling it

Most blade fuses have two small test points on top. With the circuit switched on, touch a test light to each one. If it lights on both, the fuse is good. If it lights on one side only, the fuse is blown.

Look at the blades too

Corroded or discoloured blades, or melted plastic around them, point to a poor connection heating up in the fuse box. Clean or replace the terminal, not just the fuse.

Read the full guide: blown fuse, short circuit or overload?

Colour chart

Fuse colour codes

Blade fuses are colour-coded by amp rating, and the colours are the same across ATO/ATC, Mini, Low-profile Mini, Micro2 and Micro3. Maxi fuses use their own code.

ATO/ATC, Mini, Low-profile Mini, Micro2 and Micro3

  • 1 ABlack
  • 2 AGrey
  • 3 AViolet
  • 4 APink
  • 5 ATan
  • 7.5 ABrown
  • 10 ARed
  • 15 ABlue
  • 20 AYellow
  • 25 AClear
  • 30 AGreen
  • 35 ABlue-green
  • 40 AOrange

Maxi

  • 20 AYellow
  • 30 AGreen
  • 40 AOrange
  • 50 ARed
  • 60 ABlue
  • 70 ATan
  • 80 AClear
Colour isn't enough on its own

Red is 10 A on a blade fuse and 50 A on a Maxi. Some aftermarket fuses use their own colours, too. Read the number stamped on top, and always replace a fuse with the same rating. A bigger fuse doesn't fix a problem: it lets the wire overheat instead.

Fuse taps

How a fuse tap works, and the 10-second test

An add-a-circuit fuse tap takes the place of a fuse in your fuse box. It holds the car's original fuse plus a second fuse for your new circuit, so both stay protected. It only works properly the right way round, so try it both ways below.

How an add-a-circuit fuse tap carries power From the battery (hot) To the car's circuit FUSE BOX Dash cam Power on Top slot: fuse for your new circuit Lower slot: the car's original fuse 5 10
  1. Get the right tap.Match it to the fuse type in your fuse box. Use the identifier above if you're not sure.
  2. Pick a circuit.For a dash cam, use a circuit that's only live with the key on, like the power outlet, and a constant one too if you want parking mode. Leave airbag, ABS and engine fuses alone.
  3. Find the hot side.Pull the fuse, switch the circuit on, and touch a test light to each terminal in the empty slot. The one that lights is hot.
  4. Fit the fuses.On most taps, the car's original fuse goes in the slot nearest the legs and your new fuse in the outer slot. Check the markings on yours.
  5. Do the 10-second test.With everything powered, pull the lower fuse. If your new circuit still has power, it's the right way round. If it dies, turn the tap around.

Car fuse size chart

Every common car fuse at a glance. Tap a name to open it in the identifier above.

FuseWidth × heightBladesRatingsAlso calledWhere you'll find it
ATO / ATC19.1 × 18.8 mm21 to 40 AAPR, Regular, Standard, AFOlder vehicles, trucks, RVs and add-on fuse blocks
Mini10.9 × 16.3 mm22 to 30 AATM, APM, AF2Most vehicles from the 1990s on
Low-profile Mini10.9 × 8.8 mm22 to 30 AATM-LP, APS, ATT, LP-MiniFuse boxes with little room above the fuses
Micro29.1 × 15.3 mm23 to 30 AATR, Micro 2-bladeMany newer vehicles
Micro314.3 × 15.3 mm33 to 15 AATL, Micro 3-bladeNewer vehicles. One fuse protects two circuits
Maxi29.2 × 34.3 mm2, wide20 to 80 AMAX, APX, AF3Under-hood fuse boxes
AGU glass10.3 × 38 mmMetal capsHigh currentGlass fuseOlder car audio installs
Mini ANLBolt-downSlotted tabsHigh currentMANLAmplifier power wire
ANLAbout 82 mm longBolt holesHigh currentWafer fuseMain amplifier and battery feeds

Swipe the table sideways to see every column.

Sizes are nominal, from manufacturer specifications. Blade fuse sizes are the overall width and height, blades included.

The fuses people mix up most

Most wrong fuse taps come down to one of these four.

Interchangeable

ATO vs ATC

The same fuse, really. Both are 19.1 mm wide and fit the same slots and the same fuse tap. An ATO has an open bottom, so the fuse link shows between the blades. An ATC is fully sealed, which keeps moisture out.

Open ATO / ATC
Not interchangeable

Mini vs Micro2

The big one. A Mini is 10.9 mm wide, a Micro2 9.1 mm, and the Micro2's blades are thicker and closer together. They're not interchangeable, and neither are their fuse taps. If you can't tell by eye, measure the body or use True size.

Compare them
Check the height

Mini vs low-profile Mini

Same width, different height. A low-profile Mini is only 8.8 mm tall and sits almost flush with the fuse box, where a regular Mini stands 16.3 mm tall with its blades showing. Low-profile slots take the low-profile fuse tap.

Open low-profile Mini
Different colour code

ATO vs Maxi

Same shape, very different job. A Maxi is 29.2 mm wide, rated 20 A and up, and feeds whole circuits from the under-hood box. Its colour code is different too: red is 50 A on a Maxi but 10 A on an ATO. Don't tap a Maxi slot.

Open Maxi
Troubleshooting

Got a blown fuse?

A clean break and a burnt, blackened link mean very different things. Our guide shows how to read a blown fuse, what causes shorts and overloads, and what to check before you fit a new one.

Short circuit or overload?Shop fuses and fuse taps

Common questions

What are the different types of car fuses?

Most cars use blade fuses: ATO/ATC (regular), Mini, low-profile Mini, Micro2, Micro3 and, for heavy circuits, Maxi. Under the hood you'll often also find square cartridge fuses, usually called J-Case, which we don't stock. For amplifier and accessory power wire, the usual choices are AGU glass fuses and bolt-down Mini ANL and ANL fuses.

What's the difference between ATO and ATC fuses?

Only the bottom. An ATO has an open bottom and an ATC is sealed. They're the same size, fit the same slots, and use the same fuse tap.

Is a Micro2 fuse the same as a Mini fuse?

No. A Micro2 is about 9 mm wide and a Mini about 11 mm, and the Micro2's blades are thicker and closer together. They don't fit each other's slots, so buy the fuse tap that matches.

What do the fuse colours mean?

The colour shows the amp rating. On blade fuses: grey 2 A, violet 3 A, pink 4 A, tan 5 A, brown 7.5 A, red 10 A, blue 15 A, yellow 20 A, clear 25 A and green 30 A. Maxi fuses use their own code, so always read the number stamped on top.

Can I put in a bigger fuse if one keeps blowing?

No. The fuse protects the wire. A bigger fuse lets the wire overheat instead of the fuse blowing, which is how wiring fires start. A fuse that keeps blowing means a short or too much load on that circuit, so find the cause, or ask us to.

How can I tell if a fuse blew from a short or an overload?

Look at the link. A small, clean break with a clear casing generally means over current: the circuit drew too much for too long. A burnt link with black burn marks or debris on the inside of the casing means a dead short. Intermittent shorts can sometimes leave a clean break, but short circuits are usually explosive. Blown fuse: short circuit or overload?

Which fuse tap do I need for my dash cam?

The one that matches the fuses in your fuse box. Most hardwired dash cams need two: one on a circuit that's only live with the key on, and one on a constant circuit for parking mode. Pull a fuse from the slot you plan to use and compare it here, or text us a photo.

How accurate is True size?

Once you've matched the circle to a real loonie or quarter, it's close enough to tell a Mini from a Micro2, which are about 2 mm apart. Every screen is different, so calibrate on each device you use. Your setting is remembered on that browser.

Can you install it for me?

Yes. We hardwire dash cams and install accessories, amplifiers, remote starters and alarms at our Markham shop, and every install is backed by our lifetime installation warranty. Book an installation.

Still not sure which fuse you have?

Text us a photo of the fuse and the fuse box, with your year, make and model, and we'll tell you what it is and which fuse tap fits.

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