How to Read Fuse and Appliance Labels [Safety Checklist]
Fuse ratings, cable gauge markings, and appliance rating plates are printed or stamped small, often in dark or awkward locations. Switch off and unplug before getting close, then use a phone magnifier at 4x to 8x with the flashlight on to read the amperage, voltage, wire gauge, or model data. Never open live equipment or a breaker panel's cover, and replace fuses only with the same rating and type.
Safety first, before any reading
A blown fuse, a cable you cannot identify, or an appliance that needs a replacement part all send you looking for tiny markings. Before you do, a few rules that are not optional.
- Switch off and unplug. Unplug the appliance or turn off the breaker feeding the circuit before you touch a fuse holder or look inside anything.
- Never open live equipment. Do not remove covers from anything that is plugged in or powered. Capacitors in some equipment can hold a charge even after unplugging, so if you are not trained, read the external label only.
- Breaker panels. Read the labels on the breaker switches and the panel door. Never remove the inner dead-front cover that exposes the bus bars and wiring. That is electrician work.
- When in doubt, stop. If a label is missing, burned, or you are unsure, call a qualified electrician. Nothing here replaces that.
With the power off and the equipment unplugged, reading the labels is safe and a phone makes it much easier.
Fuses: finding the amperage
Fuses come in several forms, and the rating is always printed somewhere small.
Glass cartridge fuses
Common in older appliances, audio equipment, and car accessories. The rating is stamped or printed on one of the metal end caps, for example "T 2A 250V" or "F 500mA 250V". The letter indicates the speed: T is time-delay (slow blow), F is fast-acting. The number is the current rating, and the voltage is the maximum the fuse is rated for.
The print on the end cap is tiny and on a curved reflective surface. Hold the fuse against a dark background, zoom to 6x to 8x, and angle the flashlight from the side rather than straight on. In LoupeLens, press and hold the flashlight button and swipe down to dim it so the cap does not flare white. Rotate the fuse slowly until the text lines up.
Plug-top fuses
In countries using fused plugs, the fuse is a small ceramic cartridge inside the plug, typically rated 3A, 5A, or 13A. The rating is printed on the ceramic body. Unplug first, open the plug, and read at 4x. The correct rating is also often molded into the plug itself or printed on the appliance's rating plate.
Blade fuses (automotive)
These have the amperage molded into the top of the plastic body and are color coded. The number can be hard to see on dark colors. A quick 4x zoom with the flashlight shows it clearly. Your car's manual and often the inside of the fuse box lid list which fuse protects what.
Replacing a fuse
Replace with the same rating, same speed, and same physical size. A higher rating removes the protection the fuse exists to provide, and a fuse that blows repeatedly is telling you something is wrong with the equipment, not with the fuse.
Cables: reading the jacket markings
Electrical cable is printed along its outer jacket with a string of information that repeats every meter or so. On a typical cable you will find some of the following:
- Conductor size. In North America as AWG (for example 14 AWG or 12 AWG; smaller number means thicker wire). Elsewhere as cross-section in mm squared (for example 1.5 mm2 or 2.5 mm2).
- Number of conductors. Often written as 3C or 3 x 1.5.
- Voltage rating such as 300/500V or 600V.
- Temperature rating such as 70C or 90C.
- Cable type codes such as NM-B, THHN, H05VV-F, or a national standard reference.
- Certification marks and the manufacturer's name.
The print is usually low-contrast white or gray on a white, gray, or black jacket, and it wears off with handling. To read it, find a clean section, lay it on a contrasting surface, and zoom to 4x to 5x. If the text is worn, side lighting often shows the embossed shapes even when the ink is gone. Taking a photo and then increasing contrast in Photos helps with faint print.
USB and data cables often have their rating on a small molded tag near the connector. Charging cables may list the supported wattage there. Again, 4x and the flashlight is enough.
Knowing the gauge is essential when matching an extension lead to a load, replacing a damaged cable, or checking that a previous installation used an appropriate size. If you are unsure what a marking means for your situation, that is a question for an electrician.
Appliance rating plates
Every appliance has a rating plate, a sticker or metal plate with the electrical specification and identification. It is almost never in a convenient place.
| Appliance | Typical plate location |
|---|---|
| Washing machine, dryer | Inside the door frame or on the back |
| Fridge, freezer | Inside on a side wall, or behind the kick plate |
| Oven, range | Inside the door edge or drawer |
| Dishwasher | Door edge, visible when opened |
| Microwave | Back or inside the door |
| Laptop charger | Printed on the brick, very small |
| Power tools | Motor housing, often molded |
The plate lists the voltage (for example 220-240V), the frequency (50/60 Hz), the power in watts or current in amps, and the model and serial numbers. The model number is what you need for spare parts and manuals. The serial number is for warranty and recalls. Our guide to serial and model numbers explains how to tell them apart.
To read a plate in a recessed or dark location, point the phone at it with the flashlight on, zoom to 3x to 4x, and tap to take a photo. The photo lets you step back and read it comfortably instead of crouching behind the dryer. LoupeLens puts the capture in a LoupeLens album in Photos, which is a handy place to keep a record of every appliance's model number for the day you need a part.
For an appliance you cannot move, such as a built-in oven, use the rear camera with the flashlight on. Slide the phone into the gap with the lens facing the plate, tap to take a photo, then pull the phone out and read the result.
Breaker panel labels
With the panel door open and the inner cover in place, you can safely read two things: the printed rating on each breaker's switch (15, 20, 30, and so on), and the handwritten or typed circuit directory on the door. Breaker ratings are molded into the toggle in small characters and are easy to read at 3x with the flashlight.
The circuit directory is often faded, incomplete, or wrong. Photograph it, then as you work out which breaker controls what, keep a corrected list in a note. Do not write on the panel with a pen that will smear. A fresh printed label is better.
Never remove the dead-front cover to read anything behind it. The service conductors and the incoming terminals of the main breaker stay live even when the main breaker is off. If a label is hidden behind that cover, an electrician reads it.
A short checklist
- Unplug or switch off the circuit.
- Find the label, fuse cap, or jacket print.
- Zoom to 4x (plates and cables) or 6x to 8x (fuse caps).
- Flashlight on, dimmed, angled from the side for reflective surfaces.
- Tap to photograph, then read from the photo.
- Match replacements exactly. When unsure, ask a professional.
If you work on electronics more generally, the electronics repair use case covers reading component markings on circuit boards, which follows the same principles at higher zoom.
Frequently asked questions
Where is the amperage written on a fuse?
On glass cartridge fuses it is printed or stamped on one of the metal end caps, along with the voltage and a speed letter (T for time-delay, F for fast). On plug-top fuses it is on the ceramic body. On automotive blade fuses it is molded into the top of the plastic. Zoom in at 6x to 8x with side lighting to read it.
Can I replace a blown fuse with a higher rating?
No. The fuse protects the equipment and wiring by blowing at a specific current. A higher rating removes that protection and can cause overheating or fire. Always use the same rating, speed type, and size. If fuses keep blowing, the equipment has a fault that needs repair.
How do I find the wire gauge on a cable?
It is printed along the outer jacket, repeating every meter or so, as AWG (for example 14 AWG) or cross-section in mm squared (for example 2.5 mm2). The print is low contrast and wears off, so find a clean section, zoom in at 4x to 5x, and use side light to see worn text.
Is it safe to read labels inside a breaker panel?
You can safely read the breaker switch ratings and the circuit directory with the door open and the inner dead-front cover in place. Never remove that inner cover. The service conductors and the main breaker's incoming terminals stay live even when the main breaker is off. Anything behind the cover is for a qualified electrician.