Fuses help to protect devices in a circuit against excessive current. Each fuse will display it's rated current carrying capacity on the casing. The rated current capacity is the amount of current the fuse can handle before it blows and disconnects power from the circuit. Fuses are very important in device/component protection, and should never be replaced with a piece of wire or a higher rated fuse. To check for a blown fuse, follow the steps below.
Spot a Blown Fuse
Step 1- Find the fuse box that stores the fuses.
In vehicles, fuses are usually located under the hood for high amp, and near the feet area for low amp. In some homes, there may be a fuse box located in the garage or basement.
Cartridge and screw-in type house fuses
Step 2- Remove the suspected fuse.
Find the fuse for the component that is not working and removed it from the socket. Most fuses just pull straight out, although some are screwed in or soldered into a circuit.
Step 3- Inspect the fuse.
With the fuse removed, you should now be able to spot if it has blown or not. On the blade type or clear glass tube fuses, just look inside. If the inner contact is burnt in half, or there is obvious black burn marks, then the fuse has blown.
On house type fuses, see if the glass top portion of the fuse is black and cloudy. If it is, then the fuse has likely blown.
If you are still not sure, another way to check the fuse is to meter across the two metal ends while in the Ohms setting.
Step 1- Test resistance across the fuse.
Set the multimeter to the lowest resistance setting and place one meter probe on each end of the fuse.
Step 2- Review the test results.
The meter reading should be zero Ohms resistance. If you measure high resistance or an open, then the fuse has blown.
The most important question to ask when it comes to a blown electrical fuse, is why is it failing? A fuse is designed to blow when a circuit is overloaded or shorted. If you encounter a continuously blowing fuse, you need to troubleshoot the circuit and discover the underlying problem.