How to Change a Fuse In a Fuse Box: Step-by-Step Guide

Your fuse box is hiding somewhere in your home. Look for a metal box or wooden panel with round plugs with glass circles in the center. You may find the fuse box in the basement, garage, attic, or behind a small metal door on an interior wall. Fuse panels that don’t have a box around them might be in the basement, garage, or attic.

Check the area where the electrical isn’t working to see what works and what doesn’t. Identify as many outlets and lights that don’t function as you can, and unplug any items plugged into the outlets or turn them off.

The type of fuse panel or box you have will determine how to shut off the main electrical power to the system. Look for a large switch, and flip it from the on position to off if you find one. If you find a metal handle connected to a square or rectangle box instead of a switch, grasp the handle, firmly pull the box straight out, and set it aside. The main power to the panel is now disconnected.

If you’re lucky, the fuse you’re looking for may have a label identifying the circuit it protects. If there’s no label, identify the blown fuse by looking at the center glass of each one. Look for cloudiness, scorch marks, or a missing or broken metal piece inside. Finding the blown fuse can sometimes take patience. When you locate the offending one, grasp it with your rubber-gloved hand and twist it counterclockwise to remove it from the panel. 

If you have a multimeter, check the fuse for continuity by placing one probe on the tip of the fuse and one probe on its metal screw threads. The fuse needs replacement if there’s no continuity signal or if the ohm reading is infinite or reads “OL.” 

If all of the power is out in your home, your oven, laundry appliances, or furnace, and you can’t identify one of the fuses as being blown, your main fuse or a 240V fuse may be the culprit. Use a plastic fuse puller tool to remove the cartridge fuse from the fuse block you set aside earlier, or locate another handle connected to a fuse block labeled as one of the above items and remove that fuse in the same way. Use your multimeter to check for continuity or ohms by placing the leads on the opposing fuse ends. If no continuity exists, the fuse has blown. 

To replace the fuse that’s not working, purchase or find its exact replacement. Each fuse is identifiable by type and capacity. 

If the fuse you need to replace is one of the round twist-out models, replace it by twisting the new one clockwise into the empty spot. Ensure you have the correct type by looking to see if it’s an S-type or T-type and match the number listed on its exterior, which reflects its amp rating. 

Identify and replace cartridge-type fuses by looking for the amp rating number, matching the fuse's physical size. Simply push it into place within the fuse block. Then return the block to the fuse panel by firmly sliding it into place until it can go no further. 

Fuse Types

Below are the three most common types found in fuse boxes.

• Cartridge fuses: These cylindrically shaped fuses have metal caps at both ends and a longer glass middle. You usually see these in 240-volt household circuits, and they often use 60-amp main fuses and 30 or 40-amp circuit fuses. They fit into a fuse block inserted into the box and are removable by pulling a handle. 

• Edison-base fuses: Also called Type-T, these screw-in fuses have a light bulb-style base. You find these in household circuits that can handle 125 volts maximum. The maximum rating for these fuses is 30-amps.

• Type-S: Also known as tamper-proof or rejection-base fuses, these two-part varieties have a screw-in fuse that attaches to an adapter that connects to an Edison base. The threading is unique for each fuse amperage, making it impossible to attach a fuse with an incorrect amperage capacity.

Fuse Size

You must replace any fuses with a like-for-like amperage capacity. Manufacturers print the ampere rating on the fuses for ease of reference. Installing a larger capacity fuse can overheat and damage the circuit wiring, damage any attached appliances, and create a fire risk.

When the new fuse is in place, turn the main power back on by moving the switch to the on position or re-inserting the main fuse block. Check the lights or appliances in the affected areas of the house to see if they’re working.

Occasionally, a blown fuse indicates other trouble within the electrical system. If the fuse you just swapped blows immediately after turning the main power back on, your electrical system likely has a short somewhere. Troubleshooting this situation generally requires the work of an experienced electrician. 

If the new fuse blows after turning on some lights and appliances, the problem could be in one of the items instead of the fuse itself. Replace the fuse again and then turn on one light and device at a time. If the fuse blows when a particular item is operating, the trouble is likely within that item. 

If no one item causes the fuse to blow, you may have had too many electrical devices operating simultaneously for the circuit to handle. You’ll need to reduce the load on that circuit to avoid blowing more fuses.