A voltmeter tells you whether current is flowing through a fuse

A voltmeter measures electrical voltage and can show you whether a fuse is working or blown. When you touch the voltmeter's probes to both ends of a fuse, a reading means current is flowing through it — the fuse is good. No reading means the fuse is blown and blocking current. This method works on any fuse type: blade fuses in car panels, cartridge fuses in older home panels, or ceramic fuses in appliances.

The voltmeter approach is faster than removing the fuse to look at it, because a blown fuse can look intact from the outside. It also lets you test a fuse while it sits in its holder, so you do not have to pull it out first — though you should still turn off power to the circuit before you start.

Key Takeaways

  • Set your voltmeter to DC voltage (for cars and battery-powered devices) or AC voltage (for household circuits), depending on what you are testing.
  • Touch one probe to each end of the fuse; a reading means the fuse is working, and no reading means it is blown.
  • Always turn off power to the circuit before testing, and keep your hands dry and away from live terminals.
  • A voltmeter shows whether current can flow, but does not tell you why the fuse blew — that usually means something else in the circuit is drawing too much power.

Set the voltmeter to the correct voltage type

Before you touch the probes to the fuse, turn the dial on your voltmeter to match the circuit you are testing. Most voltmeters have separate settings for AC voltage (alternating current, used in household wiring) and DC voltage (direct current, used in cars and battery-powered tools).

For a car fuse, set the dial to DC voltage — usually marked as "DCV" or "V—" on the dial. For a household fuse in a breaker panel, set it to AC voltage, marked as "ACV" or "V~". If you are not sure which one applies, check the device or panel you are testing; the voltage type is usually printed on it or in the manual.

Start with a lower voltage range — 20 volts is a safe starting point for most household and automotive circuits. If the voltmeter shows no reading, you can try a higher range, but most fuses operate well below 20 volts.

Turn off power before you test

Even though you are only measuring voltage and not working inside the panel, turning off power removes the risk of shock or accidental contact with live terminals. For a car, turn off the ignition and remove the key. For a household circuit, flip the breaker switch to the OFF position.

Wait a few seconds after turning off power. Some circuits hold a charge even after the switch is off, and waiting gives that charge time to drain. If you are testing a fuse in an appliance, unplug it from the wall outlet instead of relying on an on/off switch.

Touch the probes to both ends of the fuse

Hold the voltmeter in one hand and position its two probes so that one touches each end of the fuse. The probes are the thin metal tips at the end of the two wires coming out of the meter — usually one is red and one is black. It does not matter which probe touches which end; voltage is the same either way.

Press gently so the probe tip makes contact with the fuse terminal. You do not need to push hard — just enough to complete the circuit between the probe and the fuse. Keep your fingers on the insulated part of the probe wires, not on the metal tips.

Look at the voltmeter display. If it shows a number — any number above zero — current is flowing through the fuse and the fuse is working. If it shows zero or no reading at all, the fuse is blown and needs to be replaced.

Understand what the reading means

A voltmeter reading tells you whether a fuse is passing current, but it does not tell you why the fuse blew in the first place. Fuses blow when a circuit draws more current than the fuse is rated for — usually because a device is faulty, a wire is damaged, or something is overloaded.

If you replace the fuse and it blows again within a few days or weeks, the underlying problem is still there. Replacing it a second time without finding the cause will likely result in a third blown fuse. At that point, the circuit itself needs inspection — either by you if you have electrical knowledge, or by a technician if you do not.

Alternatives if you do not have a voltmeter

If you do not own a voltmeter, you can still check a fuse by looking at it. Remove the fuse from its holder and hold it up to a light. A blown fuse usually has a broken wire inside, visible as a gap or a blackened break in the metal filament. A working fuse shows an unbroken wire running from one end to the other.

This visual check is less reliable than a voltmeter test — some blown fuses look almost intact — but it works in a pinch. If you cannot see clearly, a magnifying glass helps. Many hardware stores and auto parts shops also have fuse testers you can borrow or buy for under ten dollars; these are simpler to use than a voltmeter and do the same job.

Safety reminders when testing fuses

Keep your hands and the voltmeter probes away from any exposed wires or terminals while power is on, even if you are only measuring. Moisture on your skin or the probes increases the risk of shock, so dry your hands before you start. Do not test a fuse if the panel or device is wet or if you are standing in water.

If you feel uncertain about where to place the probes or which circuit you are testing, stop and consult the device manual or a technician. A voltmeter is a safe tool when used correctly, but guessing at which fuse or terminal to test can lead to mistakes.

Frequently Asked Questions

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

Yes. You can touch the voltmeter probes to the metal terminals on both ends of the fuse without removing it. This is actually safer because you do not have to handle the fuse itself or disturb the holder.

What if the voltmeter shows a reading but the fuse still seems to be the problem?

A voltmeter only tells you whether current is flowing through the fuse at that moment. If the fuse is intermittently failing — working sometimes and not others — a voltmeter test might show it as good when you test it. In that case, replace it anyway and monitor whether the problem returns.

Do I need a special voltmeter for cars versus houses?

No. A standard digital multimeter (which includes a voltmeter) works for both. Just make sure you set it to DC voltage for cars and AC voltage for household circuits. Most multimeters cost between fifteen and fifty dollars and handle both types.

What voltage should I expect to see on a working fuse?

The voltage depends on the circuit. Household circuits are usually 120 or 240 volts, and car circuits are usually 12 volts. The exact reading is less important than seeing any reading at all — if the meter shows a number, current is flowing and the fuse is working.