Automotive Fuse Guide: Blade, Mini, Glass & Sizes

The automotive fuse is a sacrificial circuit-protection device. When current exceeds the fuse's rated amperage, an internal metal element melts within milliseconds, breaking the circuit before the protected wire can overheat and start a fire. Every fuse type in a modern vehicle — standard blade, mini, micro, maxi, glass SFE, ceramic, circuit breaker — does the same job through different mechanical packages and amperage ranges.

Picking the wrong type or rating is the cause of the most common automotive electrical failure pattern: the "I just keep replacing the blown fuse" loop. A blown fuse is a symptom. The root cause is either a short circuit downstream, an overloaded circuit (too many accessories added without upsizing wiring), corrosion at the fuse contact, or wear on an old fuse element. Diagnose the cause; don't just swap the fuse — and never replace a blown fuse with a higher amp rating to "stop it blowing", which removes the wire protection and creates a serious fire risk.

This guide covers the six common automotive fuse types (Standard ATO/ATC, Mini ATM, Low Profile Mini, Micro2, Micro3, Maxi APX), the universal ISO 8820 / SAE J1284 colour code amp rating system, glass SFE legacy fuses, circuit breaker fuses (Types I/II/III), the Maxi 50A red vs Standard 10A red disambiguation that catches buyers out, AU 4WD aftermarket scenarios (winch, light bar, dual battery, fridge), marine and RV requirements, and the AIMS supply story.

AIMS stocks 13+ fuse product families across Champion, Workshop Buddy, Hansa and GJ Works — covering Standard blade, Mini, Low Profile Mini, Micro, glass SFE, circuit breaker and European auto fuse kits.

Scope note: this guide covers automotive 12V/24V vehicle and equipment electrical service. Industrial HRC fuses (NH00/NH1/NH2/NH3, BS88, D-type/Diazed, switchboard rewireable) operate on different standards (AS/NZS 60269 / IEC 60269) at much higher voltages and amperages and are NOT covered here. For industrial switchboard and electrical infrastructure fuses, contact electrical wholesalers (NHP, Lawrence & Hanson, MM Electrical, CNW).

How an automotive fuse protects a circuit

A fuse contains a thin metal element (typically zinc, copper, or silver alloy) calibrated to melt at a specific current. The fuse sits in series with the protected circuit — all current to the load flows through the fuse element.

Under normal operation, the element passes current with negligible voltage drop and minimal heating. When current exceeds the fuse rating (due to a short circuit downstream, an overloaded circuit, or a stuck-on relay), the element heats rapidly, melts, and breaks the circuit. The protected wire — which is sized to carry the fuse's rated current safely — never reaches a temperature that would damage insulation or start a fire.

The wire-gauge protection principle

A fuse's amperage rating is matched to the wire gauge it protects. For example:

• 1.5mm² wire — rated for ~10A continuous service → 10A fuse
• 2.5mm² wire — rated for ~15-20A → 15A or 20A fuse
• 4.0mm² wire — rated for ~25-30A → 25A or 30A fuse
• 6.0mm² wire — rated for ~35-40A → 35A or 40A fuse

The fuse rating is always the maximum the wire can carry without overheating. Up-rating a fuse (e.g. fitting a 30A fuse where a 15A was specified) removes the protection from a 2.5mm² wire that can only safely carry 20A — the wire will overheat before the up-rated fuse blows. This is how electrical fires start in upgraded vehicles where amateurs "fixed" repeated blown fuses by going up an amp rating.

The blade fuse family — six sizes

The blade fuse is the dominant automotive fuse format since the 1970s. The family has expanded as vehicle electronics shrank — modern cars use mostly Mini and Micro fuses, but Standard and Maxi remain common for higher-amp accessories.

Type	ISO designation	Width	Amperage range	Where used
Standard / Regular	ATO (open housing) / ATC (closed housing)	19mm	1A – 40A	Older vehicles (pre-2000), AU 4WD, trucks, light commercial, accessory wiring
Mini	ATM / APM	11mm	2A – 30A	European cars from 1990s, Japanese cars from 2000s, most modern passenger vehicles
Low Profile Mini	APS	11mm (shorter blade)	2A – 30A	Modern compact European cars where space matters — same width as Mini but shorter
Micro2	ATR	9.1mm	5A – 30A	Modern Japanese/Korean cars (2010+), hybrids, EVs — even more compact than Mini
Micro3	3-blade configuration	14.4mm	5A – 15A	Modern ECM circuits requiring three-terminal control — engine + ignition + sensor circuits in newer ECUs
Maxi / Mega	APX	29mm	20A – 100A+	High-amp accessories — battery main, alternator output, winch, light bar, audio amp, dual battery systems

The ATO vs ATC distinction

ATO and ATC are both 19mm Standard blade fuses — physically and electrically interchangeable. The difference is mechanical packaging:

• ATO — open plastic housing (the original 1970s design). Element is visible through the clear plastic top.
• ATC — closed plastic housing (modern variant). Element is sealed inside, more resistant to dust, moisture and contamination.

You can fit an ATO where an ATC was, and vice versa. They are NOT separate standards. The marketplace often confuses them as different fuse types — they are the same fuse with different housings.

Mini vs Micro confusion — NOT interchangeable

Mini ATM and Micro2 ATR are both smaller than Standard but are not interchangeable. The spade geometry differs — a Micro2 will not fit a Mini socket, and a Mini will not seat properly in a Micro2 holder. Workshop reality: techs working on multiple vehicle makes commonly mis-identify these. Both blades are 11mm in length but the spades and overall width differ. Always confirm the original fuse type before sourcing replacements.

The ISO 8820 colour code amp rating chart

The universal automotive fuse colour code system is defined by ISO 8820 internationally and SAE J1284 in the US (the two are largely harmonised). The colour identifies the amp rating at a glance — across Standard, Mini, Low Profile Mini and Micro fuses, the same colour means the same amp rating. Maxi fuses use a partly different colour set because they cover higher ratings.

Standard, Mini, Low Profile Mini, Micro (ISO 8820)

Colour	Amp rating
Black	1A
Grey	2A
Violet	3A
Pink	4A
Tan / Beige	5A
Brown	7.5A
Red	10A
Blue	15A
Yellow	20A
Clear / Natural / White	25A
Green	30A
Blue-Green / Aqua	35A
Orange	40A

Maxi APX fuses — partly different colour code

Colour	Amp rating
Yellow	20A
Clear / Natural	25A
Green	30A
Orange	40A
Red	50A ⚠️ Same colour as Standard 10A
Blue	60A
Amber / Brown	70A
Clear	80A
Purple	100A

The amp number is printed on the top surface of every blade fuse. In a properly-lit workshop with good eyes, reading the printed number is more reliable than identifying the colour. In dim under-bonnet conditions or with corroded/discoloured plastic, the colour is the fallback.

Glass fuses — SFE, AGC, AGU for legacy vehicles

Glass tube fuses pre-date blade fuses and remain in service on classic vehicles (pre-1980 cars), older 4WDs, agricultural equipment, marine accessories, and some industrial machinery. Three common glass fuse standards apply:

Glass fuse type	Dimensions	Application
SFE (Standard Fuse for Electrics)	6.3mm diameter, length varies by amp (5/8" at 4A to 1-1/4" at 30A)	Classic US and AU vehicles pre-1980, legacy aftermarket accessories
AGC / 3AG	6.3mm × 32mm fixed length, all amperages same size	Electronics, audio amplifiers, marine accessories, control panels, older industrial
AGU	10.3mm × 38mm — larger glass cartridge	Higher-amp marine + audio amplifier service
MDL	6.3mm × 32mm — slow-blow variant of AGC	Motor circuits where inrush current is normal

The SFE length-by-amp trap

Unlike AGC fuses (which are all 32mm regardless of amperage), SFE fuse length increases with amperage:

• SFE 4A — 5/8" (16mm) length
• SFE 7.5A — 3/4" (19mm)
• SFE 14A — 1" (25mm) — AIMS stocks Champion SFE14
• SFE 20A — 1-1/8" (29mm)
• SFE 30A — 1-1/4" (32mm)

This means a longer SFE fuse will not fit a holder designed for a shorter (lower amp) SFE fuse. A shorter SFE will rattle loose in a holder designed for a longer fuse. Always replace SFE with the exact same amp rating — wrong-length replacement is the most common SFE installation mistake.

Ceramic 6.3mm × 32mm

Ceramic-bodied fuses to the same 6.3 × 32mm form factor as AGC are used in industrial equipment, machine tool control panels, and high-current electrical equipment where higher breaking capacity than glass is required. Common in parts washers, welders, and bench equipment. AIMS stocks 6.3A ceramic fuses as service parts for CRC SmartWasher parts washer heaters.

Circuit breaker fuses — resettable, Types I/II/III

Circuit breaker fuses are blade-format devices that look like a standard fuse but contain a thermal or electromagnetic trip mechanism instead of a meltable element. When the rated current is exceeded, the breaker trips and opens the circuit — just like a fuse — but can be reset rather than replaced.

Type	Reset method	Best for
Type I (Auto-Reset)	Cools and resets automatically after current drops below rating	Power windows, sunroof motors, electric seats — any circuit where intermittent trips during normal use are expected
Type II (Modified Reset)	Holds tripped while power is applied; resets when power is removed	Trailer plug accessories, some audio circuits — won't auto-cycle but resets without manual intervention
Type III (Manual Reset)	Push-button manual reset required after trip	4WD winches, light bars, dual battery systems, audio amplifiers — applications where the operator needs to know a trip occurred and physically inspect before resetting

Common amp ratings: 10A, 15A, 20A, 25A, 30A, 35A, 40A, 50A. Available in Standard ATO and Mini ATM blade form factors so they drop into existing fuse panels.

The Champion CA113 Circuit Breaker Fuse Assortment Kit contains 35 pieces across all three Types and a range of amperages — the AU workshop standard for fitting circuit breakers in place of conventional fuses on aftermarket installations.

How to read an automotive fuse — colour + number + size

Three pieces of information identify any automotive fuse:

1. Size family — Standard (19mm), Mini (11mm), Low Profile Mini (11mm short blade), Micro2 (9mm), Micro3 (3-blade), or Maxi (29mm). Hold the fuse against a known reference if uncertain.
2. Amp rating — colour code per the ISO 8820 chart above, AND the number printed on the top of the fuse. Use both. If they disagree (unusual but happens with counterfeit/budget fuses), trust the printed number.
3. Voltage rating — most automotive blade fuses are rated to 32V DC, suitable for 12V and 24V vehicle electrical. Glass fuses for marine + audio service may be rated 250V AC (these are not interchangeable with automotive blade fuses despite the similar amperages — different breaking capacity).

Testing a fuse — visual vs multimeter

Visual inspection of a blade fuse looks at the U-shaped element through the clear plastic top. A blown fuse normally shows the element broken or melted apart — easy to see.

However, modern fuses can develop hairline fractures in the element that are invisible to the eye but break the circuit electrically. The reliable test is a multimeter continuity check:

1. Remove the fuse from the circuit (don't test in-circuit — adjacent circuits can give false readings)
2. Set multimeter to continuity (beep) mode or low-range ohms
3. Touch one probe to each spade — a good fuse beeps / reads near 0 ohms; a blown fuse reads OL (open line) / infinite resistance

A second multimeter check worth doing on an installed fuse: voltage drop across the fuse. With the circuit live and drawing current, the voltage drop across the fuse should be near zero (millivolts). A significant drop (0.1V+) indicates corrosion at the spade-to-socket interface even if the fuse element is intact — clean the socket and re-test.

Why fuses blow — and what to do about it

A blown fuse is the symptom. The root cause is one of five things:

Cause	Diagnosis	Fix
Short circuit — bare wire touching ground	Fuse blows instantly when circuit is energised. Replacement also blows. Often after recent work in the area.	Trace the wiring; find and repair the short before fitting a new fuse.
Overload — too many accessories on one circuit	Fuse blows during heavy use (everything on, winch running, etc.) but not at rest.	Reduce load, or split into multiple circuits with separately-fused supplies. Don't up-rate the fuse.
Faulty appliance / motor	Single component on the circuit (winch, blower motor, water pump) draws excess current when operated.	Test the component current draw with a clamp meter under load. Replace the faulty component.
Corroded contacts	Intermittent operation. Fuse element appears intact but voltage drop across the fuse is high. Common on marine, AU 4WD heavy-use vehicles.	Clean spade contacts and socket with contact cleaner; replace if pitted. Consider sealed/marine fuse holder for corrosive environments.
Fuse fatigue — element thinned by repeated near-rated current cycling	Fuse blows at rated current after years of close-to-limit service.	Replace with same rating; consider whether circuit design is running too close to fuse rating (add headroom).

AU 4WD + aftermarket installations

The Australian 4WD aftermarket adds load to vehicle electrical systems that the factory wiring + fuses were never designed for. Winch, dual battery, fridge, light bar, UHF radio, recovery air compressor, inverter, fridge slide power — every accessory adds amps.

Typical aftermarket amperage

Accessory	Typical current draw	Recommended fuse / breaker
9000-12000 lb winch	250-450A peak under load	Maxi 100A+ or auto-reset circuit breaker
40+ inch LED light bar	15-25A at full power	30A Standard or 30A Maxi with relay
Dual battery isolator	30-100A depending on size	Maxi 50-100A or anchor stud
12V fridge (Engel, ARB, Waeco)	5-10A continuous, 12A startup	15A Standard or 15A Mini per fridge
UHF radio	2-5A transmit	10A Standard or 10A Mini
1500W inverter	120A+ at full output	Maxi 150A or sub-feed circuit breaker
Recovery air compressor	20-30A	30A Standard or Type I auto-reset breaker
HID work light (older)	3-5A	10A Standard

Why circuit breakers, not fuses, on AU 4WD accessory circuits

Circuit breakers (especially Type I auto-reset and Type III manual reset) are preferred over fuses on aftermarket 4WD installations because:

• Resettable — a brief overload (winch under load, light bar momentary spike) doesn't strand the vehicle waiting for a fuse replacement
• Sealed housings available — better for dust, mud, river crossings
• Manual reset (Type III) provides operator awareness — when a trip happens, the operator knows about it and can investigate (a fuse just silently blows)
• Higher cycle life than repeatedly-replaced fuses

AIMS stocks the Champion CA113 Circuit Breaker Fuse Assortment Kit (35 pieces across Types I/II/III) for AU 4WD aftermarket installations.

Marine and RV — sealed fuses for corrosion resistance

Salt water, salt air, and humidity destroy standard blade fuses within months of marine service. The brass spade contacts corrode, the socket spade clips corrode, voltage drop increases, and eventually the circuit becomes intermittent or fails completely.

Marine and RV electrical installations should use:

• Sealed-housing ATC fuses instead of open-housing ATO — the closed plastic resists moisture ingress to the element
• Tin-plated spades where available — slows corrosion compared to plain brass
• Marine-grade fuse holders with rubber boots over the spade connections
• Stainless steel-tin contact ANL-style fuses for high-amp DC main circuits (battery to bus, alternator output) — the marine standard for severe service
• Annual inspection — visual check + voltage-drop test on every accessible fuse holder

Standard automotive ATO blade fuses installed in marine service typically last 12-24 months before corrosion-related issues appear. Sealed ATC + marine-grade holders extend that to 5+ years in typical AU coastal service.

Fuse holders, distribution blocks + auxiliary panels

For aftermarket installations — auxiliary lights, dual battery isolators, fridge slides, UHF radios, light bars — the standard pattern is to fit a separate fuse panel rather than tapping into the factory fuse box. This keeps factory wiring untouched, allows correct fuse sizing per accessory, and concentrates the aftermarket protection in one accessible location.

Inline fuse holders

Inline blade fuse holders accept a Standard ATO/ATC blade fuse in a sealed waterproof housing with a 12-15A or 20-30A wire pigtail. Used for single-accessory installations where running a dedicated wire from battery to accessory is cleaner than re-using the factory fuse panel. Most have rubber boots over the spade contacts and IP65+ sealing for under-bonnet, under-vehicle and engine bay use.

Surface-mount fuse panels (6-way, 8-way, 12-way)

Multi-circuit fuse panels mount on a bracket near the auxiliary battery or in the cargo area, with screw terminals for each protected circuit. A single fat positive feed from the battery (typically Maxi or ANL-fused at the battery) supplies the panel; the panel distributes through individual blade fuses to each accessory. The AU 4WD aftermarket standard for serious dual battery and fit-out installations.

Auxiliary switch panels

Switch panels combine fused circuits with rocker switches in a single unit — typically 4 or 6 switches each protected by its own blade fuse. Mounted on the dash or overhead console, they consolidate aftermarket controls (driving lights, light bar, work lights, fridge, UHF). The fuse rating per switch matches the wire gauge to that switch.

AIMS does not currently stock dedicated fuse holders, distribution panels or switch panels — these are sourced through 4WD aftermarket specialists (REDARC, Projecta, Narva, Hulk 4x4, ARB). The blade fuses and circuit breaker fuses that go into these panels are the AIMS supply story.

Fuse replacement procedure

1. Identify the blown fuse — locate the fuse box (under-dash, under-bonnet, under-seat in some 4WDs; both locations on many modern vehicles). Most factory fuse boxes have a printed diagram showing which fuse protects which circuit.
2. Remove the fuse — use a fuse puller tool (most factory fuse boxes include one clipped inside the lid). Long-nose pliers work in a pinch but risk damaging adjacent fuses.
3. Confirm size and rating — note the fuse SIZE (Standard / Mini / Low Profile Mini / Micro2) and AMP rating (colour + printed number).
4. Test the removed fuse — multimeter continuity. If the fuse is good, the problem is elsewhere (corroded socket, broken wire, faulty relay).
5. Source the correct replacement — same size, same amp rating. AIMS stocks Champion Standard blade kits, Mini kits, Low Profile Mini kits, and Workshop Buddy + Hansa equivalents.
6. Inspect the socket before fitting the new fuse — clean any visible corrosion with contact cleaner; if the socket spade clips look pitted or sprung, the holder may need replacement.
7. Fit the new fuse — press firmly until fully seated. Test the protected circuit.
8. If the new fuse blows immediately — STOP. There is a short circuit downstream. Do not keep replacing. Trace the wiring to find the fault before fitting another fuse. (Repeated blown fuses is the second-most-common cause of vehicle fires.)
9. Restock the spare — most factory boxes have a spare fuse holder. Replace it from your assortment kit so the next blown fuse can be replaced from on-board stock.

AIMS supply — Champion + Workshop Buddy + Hansa

AIMS stocks 13+ automotive fuse product families across four trade brands. The range covers Standard blade, Mini, Low Profile Mini, Micro, European auto, glass SFE, and circuit breaker assortments — the comprehensive workshop stock for AU automotive electrical service.

Champion (AU industrial trade) — dominant range

• Champion CA110 Blade Fuse Assortment Kit 3-30A — 110 pieces (Standard ATO blade, 49 units)
• Champion CA111 Low Profile Mini Blade Fuse Kit — 120 pieces (30 units)
• Champion CA112 Auto Mini Blade Fuse Kit — 120 pieces (Mini ATM, 13 units)
• Champion CA113 Circuit Breaker Fuse Assortment Kit — 35 pieces (Types I/II/III, 24 units — premium kit)
• Champion CA2005 Auto Fuse Master Kit (multi-size master, 33 units)
• Champion CA2385 Blade Fuse Master Assortment Kit (50 units — flagship workshop master kit)
• Champion C2385-1 Blade Fuse Mini 4A (15/pack — individual mini fuses)
• Champion C2385-2 Blade Fuse Micro 4A (15/pack — individual micro fuses)
• Champion SFE14 Glass Fuse 14A (50/pack — legacy SFE)

Workshop Buddy (AU automotive trade)

• Workshop Buddy Car Fuse Grab Kit 5-30A — 120 pieces (Standard ATO blade)
• Workshop Buddy Mini Car Fuse Grab Kit 5-30A — 120 pieces (Mini ATM)
• Workshop Buddy European Auto Fuse Grab Kit 5-30A — 120 pieces (European-spec Mini)

Hansa

• Hansa MFA-100 Mini-Blade Fuse Assortment Kit — 100 pieces (33 units)

Honest scope — NOT stocked, sourced through supplier network on request

• HRC industrial fuses (NH00, NH1, NH2, NH3) — different scope, AS/NZS 60269 — direct to electrical wholesalers
• BS88 cartridge industrial fuses — same as above
• D-type / Diazed switchboard plug fuses — electrical wholesale scope
• Solar/PV DC fuses (mPV) and dedicated solar fuse holders
• Maxi/ANL high-amp marine-rated bolt-down fuses (large DC main protection)
• Fuse holders sold separately (in-line, panel mount, ANL) — direct to auto-electrical specialists
• Slow-blow industrial fuses
• Semiconductor-rated industrial fuses

For any of these, contact our team or call (02) 9773 0122 with the specification + application and we'll quote through our supplier network.

Selection checklist — 7 questions before ordering

1. What size? Standard (19mm), Mini (11mm), Low Profile Mini (11mm short blade), Micro2 (9mm), Micro3 (3-blade), or Maxi (29mm)?
2. What amp rating? Match the original fuse exactly — read both the colour and the printed number. Never up-rate.
3. How many do you need? Individual replacement (a few of one size) or workshop master kit (full range)?
4. Is the original a circuit breaker? Some factory installations and most AU 4WD aftermarket use circuit breaker fuses — replace with same Type (I/II/III) and amp rating, not a meltable fuse.
5. Marine or salt-exposed environment? Specify sealed-housing ATC and consider marine-grade fuse holders for the protected circuits.
6. Modern hybrid/EV — Micro2 or Micro3? Modern Japanese hybrids and EVs use these — verify before sourcing.
7. Aftermarket high-amp accessory? Winch, light bar, dual battery, inverter — likely needs Maxi or Type III manual-reset breaker, not Standard blade.

For workshop kit selection, brand cross-reference, or unusual fuse types, contact our team or call (02) 9773 0122.

Frequently asked questions

What are the different types of automotive fuses?

Six blade fuse sizes are common in modern vehicles: Standard (ATO open housing / ATC closed housing, 19mm wide, 1-40A), Mini (ATM/APM, 11mm, 2-30A), Low Profile Mini (APS, same width as Mini but shorter blade, 2-30A), Micro2 (ATR, 9mm, 5-30A — newer Japanese/Korean cars), Micro3 (3-blade, modern ECM circuits), and Maxi (APX, 29mm, 20-100A+ for high-amp accessories). Plus glass tube fuses (SFE, AGC, AGU) for legacy vehicles and ceramic 6.3×32mm for industrial equipment. Circuit breaker fuses look like blade fuses but are resettable rather than meltable.

What is the colour code for automotive fuses?

ISO 8820 / SAE J1284 defines the standard automotive blade fuse colour code: 1A black, 2A grey, 3A violet, 4A pink, 5A tan, 7.5A brown, 10A red, 15A blue, 20A yellow, 25A clear/natural, 30A green, 35A blue-green, 40A orange. The same colour means the same amp rating across Standard, Mini, Low Profile Mini and Micro fuse sizes. Maxi fuses use a partly different colour set because they cover higher ratings (50A red, 60A blue, 70A amber, 80A clear, 100A purple). The amp number is also printed on top of every fuse — read it as well as the colour.

ATO vs ATC fuses — what's the difference?

ATO and ATC are both 19mm Standard blade fuses and are physically and electrically interchangeable. The difference is mechanical packaging: ATO uses an open plastic housing (the original 1970s design with the element visible through clear plastic on top), while ATC uses a closed plastic housing that completely seals the element. Both fit the same fuse holders and have identical amp ratings per colour. ATC is preferred for marine, RV, off-road and any environment with dust, moisture or contamination because the sealed housing extends service life. You can fit ATO where ATC was, and vice versa.

Are Mini and Micro fuses interchangeable?

No. Mini ATM and Micro2 ATR are both smaller than Standard blade fuses but are NOT interchangeable. The spade geometry and overall dimensions differ — a Micro2 will not fit a Mini socket, and a Mini will not seat properly in a Micro2 holder. Mini fuses are 11mm wide; Micro2 are about 9mm wide. The workshop reality is that techs working on multiple makes commonly mis-identify these. Always confirm the original fuse type (visual match against the factory-fitted fuse, or check the vehicle service manual) before sourcing replacements.

Can I use a higher amp fuse?

Never. The fuse rating is matched to the wire gauge it protects. For example, a 15A fuse typically protects 2.5mm² wire rated to about 20A. Fitting a 30A fuse where a 15A was specified removes all protection — the wire will reach 200°C+ and melt the insulation before the 30A fuse blows, starting an electrical fire. If a circuit keeps blowing fuses, the problem is either a short circuit downstream or genuine overload — diagnose and fix the cause, don't up-rate the fuse. If you genuinely need more capacity for an aftermarket accessory, run a new, larger-gauge circuit with a fuse correctly sized for the new wire gauge.

Why does my car fuse keep blowing?

A repeatedly-blown fuse means there's an underlying fault — most commonly a short circuit (bare wire touching ground or another conductor), an overloaded circuit (too many accessories drawing combined current above the fuse rating), a faulty appliance drawing excess current, corroded contacts at the fuse holder, or fuse fatigue from years of close-to-rated cycling. Replace the fuse once with the correct rating — if it blows again, do NOT fit a higher amp fuse. Diagnose the cause: test the circuit with the load disconnected (does the fuse hold? then load is the issue) or with a multimeter checking for shorts to ground.

How do I test a blade fuse?

Two methods. Visual: pull the fuse, look through the clear plastic top — the U-shaped element should be intact. A blown fuse shows the element broken or melted apart. However, modern fuses can have invisible hairline fractures that break the circuit electrically but look fine. Reliable method: multimeter continuity test. Remove the fuse from the circuit, set the multimeter to continuity (beep) or low-range ohms, touch one probe to each spade — a good fuse beeps or reads near 0 ohms; a blown fuse reads OL (open line) or infinite resistance. Also worth doing on installed fuses: voltage drop across the fuse under load — should be near zero (millivolts); significant drop indicates corrosion at the spade contact even if the element is intact.

What is an SFE fuse?

SFE (Standard Fuse for Electrics) is the original American glass tube automotive fuse standard, used widely in pre-1980 cars and still found in classic vehicles, older 4WDs, and some legacy accessory installations. SFE fuses have a 6.3mm diameter glass tube. Unique to SFE: the LENGTH varies with amp rating — 4A is 5/8" (16mm), 7.5A is 3/4" (19mm), 14A is 1" (25mm), 20A is 1-1/8" (29mm), 30A is 1-1/4" (32mm). A longer SFE won't fit a holder designed for a shorter (lower amp) one, and a shorter SFE will rattle loose in a holder for a longer one. Always replace SFE with the exact same amp rating. AIMS stocks Champion SFE14 (14A) for legacy vehicle service.

What's a Maxi fuse?

Maxi (also called APX) is a larger 29mm-wide blade fuse used for high-amp accessory protection — typically 20A to 100A+. Common applications: battery main circuits, alternator output, winch supply circuits, large LED light bar installations, dual battery isolators, inverters, audio amplifier circuits. Maxi uses a partly different colour code from Standard/Mini/Micro because it covers higher amp ratings — critically, Maxi 50A is RED, the same colour as Standard 10A. Always confirm the fuse SIZE first (Standard vs Mini vs Maxi) before identifying amperage by colour, and read the number printed on the top of the fuse.

How do I replace a car fuse?

(1) Identify the blown fuse — locate the fuse box (under-dash, under-bonnet, sometimes under-seat) and check the diagram for which fuse protects which circuit. (2) Use a fuse puller (clipped inside most factory fuse box lids) to remove the fuse. (3) Note the fuse size (Standard / Mini / Low Profile Mini / Micro2) and amp rating (colour + printed number). (4) Test the removed fuse with a multimeter to confirm it's actually blown. (5) Fit a replacement of EXACTLY the same size and amp rating — never up-rate. (6) Check the socket for corrosion; clean with contact cleaner if needed. (7) Test the protected circuit. (8) If the new fuse blows immediately, STOP — there is a short circuit downstream. Diagnose before fitting another fuse. (9) Restock the spare in the factory holder so the next blown fuse can be replaced from on-board stock.

What's a circuit breaker fuse?

A circuit breaker fuse is a blade-format device that looks like a standard fuse but contains a thermal or electromagnetic trip mechanism instead of a meltable element. When the rated current is exceeded, the breaker trips and opens the circuit — just like a fuse — but can be reset rather than replaced. Three types: Type I auto-reset (cools and resets automatically — best for power windows, sunroof motors, electric seats where intermittent trips are expected); Type II modified reset (holds tripped while power applied, resets when power removed — best for trailer plug accessories); Type III manual reset (push-button reset required — best for 4WD winches, light bars, dual battery systems where operator awareness of trips matters).

Are car fuses the same in all vehicles?

No. While the standard fuse types (Standard ATO/ATC, Mini, Micro) are universal across manufacturers, different vehicles use different fuse sizes in different positions. Older vehicles (pre-2000) mostly use Standard blade. European cars from the 1990s onwards use Mini almost exclusively. Modern Japanese and Korean cars (2010+) increasingly use Micro2 and Micro3. Modern hybrid and electric vehicles use a mix of all sizes plus specialty fuses for the high-voltage battery system. Always check the factory fuse box diagram or vehicle service manual to confirm which size and amperage is specified for each circuit.

What size fuse for a 12V LED light bar?

Depends on the light bar's current draw — typically 15A for smaller (20-30 inch) bars drawing ~12A, 20A for medium (40-50 inch) bars drawing ~18A, and 30A for large (40"+) bars drawing ~25A. Look up the manufacturer's specification — most LED light bars draw less than their headline wattage divided by 12V because the LED driver is efficient. Wire gauge must match the fuse rating: 2.5mm² for 15-20A, 4mm² for 25-30A. For installations switched by a relay (recommended), the fuse protects the supply circuit from battery to relay — sized for the light bar load. AIMS stocks Champion CA110 Blade Fuse Assortment Kit with 15A, 20A, 25A and 30A blade fuses for these applications.

What's the difference between automotive and industrial fuses?

Automotive fuses operate at 12V or 24V DC and use the ISO 8820 / SAE J1284 standards — blade format, glass tube SFE/AGC, with amperage ratings up to about 100A and breaking capacities suited to vehicle electrical systems. Industrial fuses (HRC types like NH00/NH1/NH2/NH3, BS88 cartridge, D-type Diazed) operate at much higher voltages (typically 415V AC for industrial AC distribution), much higher amperages (up to thousands of amps), with much higher breaking capacity (typically 80kA+). Industrial fuses are governed by AS/NZS 60269 / IEC 60269. They are NOT interchangeable with automotive fuses and serve completely different applications. AIMS stocks automotive only — for industrial HRC, source through electrical wholesalers (NHP, Lawrence & Hanson, MM Electrical).

What's a good workshop fuse kit?

For a small AU workshop or auto-electrical service van, the Champion CA110 Blade Fuse Assortment Kit (110-piece, 3-30A across Standard blade) and CA112 Auto Mini Blade Fuse Kit (120-piece, Mini) cover most modern vehicle service. Add the CA113 Circuit Breaker Fuse Assortment Kit for AU 4WD aftermarket installations. For larger workshops or vehicles spanning Standard + Mini + Micro coverage, the Champion CA2385 Blade Fuse Master Assortment Kit is the flagship workshop master kit. The Workshop Buddy grab kits offer specialised coverage — Car Fuse (Standard), Mini Car Fuse (Mini), and European Auto (European-spec Mini).

For rust removal, conversion and corrosion-prevention products, see the AIMS Rust Treatments range.