How to Replace a Fuse in a Fuse Box

If your home was built before the 1960s, there's a good chance it has a fuse box instead of a modern circuit breaker panel. When a fuse blows, the circuit loses power — and unlike a breaker, you can't just flip a switch. You need to replace the fuse.

The good news: replacing a fuse is one of the simplest electrical repairs a homeowner can do. Here's exactly how to do it safely.

Types of Fuses in a Home Fuse Box

Before you start, it helps to know which type of fuse your box uses:

Plug fuses (Edison-base): Screw in like a light bulb. The most common type in older homes. You can see the fuse element through a small glass window.
Type S fuses (tamper-resistant): Similar to plug fuses but require a matching adapter base — designed to prevent installing the wrong amperage.
Cartridge fuses: Cylindrical fuses that pull out of clip holders. Used for high-amperage circuits like electric ranges and dryers (30A–60A).
Glass tube fuses (5x20mm): Small cylindrical fuses found in appliances, electronics, and some older panel sub-circuits.

What You'll Need

Klein Tools NCVT1P Non-Contact Voltage Tester — verify which parts of the fuse box are energized before touching anything.
AstroAI Digital Multimeter — test fuses for continuity to confirm which one has blown, especially for cartridge fuses you can't inspect visually.
300Pcs 5x20mm Glass Fuse Assortment (250V, 0.1A–20A) — covers the full range of glass tube fuse ratings for appliances and sub-circuits.
Fuse puller or needle-nose pliers — for safely removing cartridge fuses
Flashlight — fuse boxes are often in dim utility areas
Rubber-soled shoes and dry hands

Step-by-Step: How to Replace a Fuse in a Fuse Box

Step 1: Cut Power to the Affected Area

Turn off or unplug all devices in the room or area that lost power. This reduces the load on the circuit so the new fuse doesn't blow immediately after installation.

Step 2: Locate the Fuse Box

Fuse boxes are typically found in utility rooms, basements, hallways, or garages. Open the box door. Use a flashlight if needed — good visibility is important for safe fuse work.

Step 3: Identify the Blown Fuse

For plug fuses: Look through the small glass window on each fuse. A blown fuse will show one of these signs:

A broken or melted wire element inside the glass
A blackened, cloudy, or discolored window (indicates a short circuit or arc)
A clean break with a clear window (indicates a simple overload)

For cartridge fuses: Visual inspection is unreliable. Use your multimeter set to continuity mode — touch one probe to each metal end cap. A good fuse beeps; a blown fuse shows no continuity (open circuit).

For glass tube fuses: Same as cartridge — test with the multimeter continuity function. You may also see a broken wire inside the glass tube on close inspection.

Step 4: Check the Amperage

Before removing the fuse, note the amperage printed on it. This is critical — you must replace it with the exact same rating. Common household fuse ratings:

15A: General lighting and outlet circuits
20A: Kitchen appliance circuits
30A: Electric dryer, water heater
60A: Electric range, main disconnect

Step 5: Remove the Blown Fuse Safely

Plug fuse: Grip the insulated rim (not the metal base) and unscrew counterclockwise. The fuse box may still be partially energized — use your non-contact voltage tester to check the socket before reaching in.

Cartridge fuse: Use a fuse puller tool or needle-nose pliers to grip the fuse body and pull it straight out of the spring clips. Never use bare hands — cartridge fuses in high-amperage circuits may still be energized even with the main switch off.

Glass tube fuse: If in a fuse holder, twist or pull the holder cap to access the fuse, then remove it by hand or with needle-nose pliers.

Step 6: Install the Replacement Fuse

Select the replacement fuse with the exact same amperage rating as the blown one. Never install a higher-rated fuse — this is the most dangerous mistake in fuse replacement and a leading cause of electrical fires.

Plug fuse: Screw the new fuse in clockwise until snug. Don't overtighten.
Cartridge fuse: Push the new fuse firmly into the spring clips until both ends are fully seated.
Glass tube fuse: Insert into the holder and secure the cap.

For glass tube fuses, select the correct rating from your 300-piece glass fuse assortment — it covers 15 values from 0.1A to 20A at 250V.

Step 7: Restore Power and Test

Close the fuse box. Restore power to the area by turning on lights or plugging in a lamp. If power is restored and the fuse holds, you're done.

If the fuse blows again immediately, stop. There's an underlying fault — a short circuit, ground fault, or faulty appliance — that must be diagnosed before replacing the fuse again. Check for overloaded circuits, short circuits, or faulty appliances as the root cause.

The Golden Rule of Fuse Replacement

Always replace a fuse with the exact same amperage rating. Installing a higher-rated fuse (e.g., a 20A fuse in a 15A circuit) allows more current to flow than the wiring can safely handle. The wiring overheats, the insulation melts, and a fire can start inside your walls — with no fuse to stop it.

When to Consider Upgrading to a Breaker Panel

If your home still has a fuse box, it may be worth upgrading to a modern circuit breaker panel, especially if:

Fuses blow frequently
You're adding new circuits or high-draw appliances
The fuse box is old, corroded, or has signs of overheating
Your homeowner's insurance requires it (some insurers won't cover homes with fuse boxes)
You want the convenience of resettable breakers

A panel upgrade typically costs $1,500–$4,000 and must be done by a licensed electrician.

Frequently Asked Questions

Can I replace a fuse myself?

Yes — replacing a plug fuse or glass tube fuse is a straightforward DIY task. Cartridge fuses in high-amperage circuits (30A+) carry more risk and require more caution. If you're unsure, call an electrician.

How do I know what amperage fuse to buy?

The amperage is printed on the blown fuse itself. If the fuse is too damaged to read, check the fuse box label or the circuit's wiring gauge (14 AWG = 15A max, 12 AWG = 20A max). Never guess — always match exactly.

Why does my fuse keep blowing?

A fuse that blows repeatedly signals an underlying problem: overloaded circuit, short circuit, ground fault, or faulty appliance. Identify and fix the root cause before replacing the fuse again. Check for overloaded circuits, short circuits, or faulty appliances as the most common causes.

Is a fuse box dangerous?

A properly maintained fuse box with correctly rated fuses is safe. The danger comes from improper fuse replacement (wrong amperage), DIY modifications, or an aging box with corroded connections. Have an electrician inspect your fuse box if it's old or showing signs of wear.

Quick Recap

Turn off devices on the affected circuit
Locate the fuse box and identify the blown fuse (visual or multimeter test)
Note the amperage before removing
Remove the blown fuse safely (unscrew or pull out)
Install the exact same amperage replacement
Restore power — if it blows again, diagnose the root cause

Keep a glass fuse assortment kit and a multimeter in your home toolkit — they make fuse diagnosis and replacement fast, safe, and accurate.

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