A fuse is working if your multimeter shows continuity; a blown fuse shows no continuity

A multimeter is a handheld tool that measures electrical properties. When you test a fuse with one, you are checking whether electricity can flow through it. A working fuse will show a reading close to zero ohms (the unit of electrical resistance). A blown fuse will show infinite resistance or no reading at all, meaning the wire inside has broken and electricity cannot pass through.

The multimeter has a dial or digital display with different settings. To test a fuse, you set it to the ohms setting — usually marked with the Greek letter omega (Ω) — and touch the two metal probes to each end of the fuse. If the fuse is good, the meter beeps or shows a number near zero. If the fuse is blown, the meter shows nothing or a very high number.

Key Takeaways

  • Set your multimeter to the ohms (Ω) setting before touching the fuse with the probes.
  • A working fuse shows a reading near zero ohms; a blown fuse shows infinite resistance or no reading.
  • Always remove the fuse from the circuit or device before testing it — testing a fuse while it is still connected can damage the multimeter.
  • The metal caps on each end of the fuse are what you touch with the probes, not the ceramic or plastic body.

Why you need to remove the fuse first

Testing a fuse while it is still plugged into a circuit or installed in a device can send electrical current back into your multimeter and damage it. The fuse must be physically removed and sitting on a table or in your hand before you test it.

If you are testing a fuse in a car, unplug the negative battery terminal first. If you are testing a fuse in a home circuit breaker box or appliance, turn off the power to that circuit at the main switch. Wait a few seconds to make sure power has drained, then remove the fuse.

The step-by-step process

Step 1: Set the dial to ohms. Look at your multimeter's dial or digital screen. Find the ohms setting, marked with Ω. If your multimeter has multiple ohm ranges (like 200Ω, 2000Ω, 20kΩ), start with the middle range. Digital multimeters often auto-detect the range, so you may only see one Ω option.

Step 2: Touch the probes to the fuse ends. The multimeter has two probes — one red and one black. Touch the red probe to one metal cap on the fuse and the black probe to the other metal cap. It does not matter which probe goes on which end.

Step 3: Read the display. Look at the number on the screen or listen for a beep. A working fuse shows a reading between 0 and 1 ohm, or the meter beeps. A blown fuse shows no number, a very high number (often displayed as "1" or "OL" for overload), or no beep.

What the readings actually mean

When your multimeter shows a number close to zero, that means electricity flows freely through the fuse — it is working. The tiny resistance you see (like 0.5 ohms) is normal and does not mean the fuse is bad.

When your multimeter shows nothing, a dash, "OL", or a very high number like 999, that means no electricity can flow through. The fuse wire has burned out and the fuse is blown. This is the fuse you need to replace.

Some multimeters have a continuity setting separate from ohms — it looks like a sound wave symbol. If your meter has this, you can use it instead. Continuity mode beeps when electricity can flow and stays silent when it cannot. This is often easier to read than watching numbers.

Common mistakes that give wrong readings

The most common error is touching the ceramic or plastic body of the fuse instead of the metal caps. The body is an insulator, so your meter will show infinite resistance even if the fuse is good. Always touch only the shiny metal ends.

Another mistake is testing a fuse that is still in the circuit. This can damage your multimeter or give a false reading because current is flowing through the fuse from the power source. Remove it completely first.

If your multimeter is set to the wrong range, you might see a reading that does not make sense. If you are testing a car fuse and the meter shows a very high number, try switching to a lower ohm range (like 200Ω instead of 2000Ω) and test again.

When to replace a fuse versus when to investigate further

If your multimeter shows the fuse is blown, you can replace it with a new fuse of the same amperage rating. The amperage is printed on the fuse itself — common ratings are 5A, 10A, 15A, or 20A. Always use the exact same rating.

If you replace the fuse and it blows again when ready, something else in the circuit is wrong — usually a short circuit or an overloaded wire. Do not keep replacing fuses. A fuse that blows repeatedly is a sign to have an electrician or mechanic look at the circuit, not a reason to use a higher-amperage fuse.

Multimeters that make this easier

Digital multimeters with an auto-ranging feature do most of the dial-setting work for you. You set it to ohms once and it picks the right range automatically. These cost between $20 and $50 and are worth the difference if you plan to test fuses more than once.

Multimeters with a dedicated continuity setting (the sound wave symbol) are easier to read than watching a number change. You hear a beep for a good fuse and silence for a blown one, which takes the guesswork out of reading the display.

Analog multimeters (with a needle instead of a digital display) work the same way but require you to read where the needle points. They are less common now and harder to read accurately, so a digital multimeter is the better choice if you are buying one for the first time.

Frequently Asked Questions

Can I test a fuse while it is still in the device?

No. Testing a fuse while it is connected to power can damage your multimeter or give a false reading. Always remove the fuse from the circuit first, then test it on a table or in your hand.

What does it mean if the multimeter shows a number like 0.3 ohms?

That is a good fuse. Any reading between 0 and 1 ohm means electricity flows through freely. The small number is just the natural resistance of the metal, which is normal and expected.

My multimeter shows "OL" — is the fuse definitely blown?

Probably, but check that you are touching the metal caps at the ends of the fuse, not the ceramic body. If you are touching the caps and still see "OL", the fuse is blown and needs to be replaced.

Do I need a special multimeter to test car fuses versus home fuses?

No. Any standard digital multimeter works for both. Car fuses and home fuses are tested the same way — set to ohms, touch the probes to the metal ends, and read the display.

What if I do not have a multimeter — how else can I tell if a fuse is blown?

You can look at the fuse under bright light. A blown fuse has a broken wire visible inside the glass or plastic tube, or the inside is blackened or discolored. A good fuse has a thin wire running straight across the inside with no breaks or burn marks.