Heavy Duty 200A Automotive Bolt-on Bolt-down Fuse 80V dc For Electric Forklift Battery Charger Pallet Truck Golf Cart

Most of us have experienced a blown fuse at one time or another and simply replaced it. Some fuses, though, aren't cheap and if a replacement isn't handy it means a trip to the auto parts or home improvement store. As a professional electrician I have had to test many fuses over the years; it is a standard part of troubleshooting techniques rather than simply replacing fuses that I don't know for sure are blown.
Better to test a fuse first to see if it is actually blown before making a special trip to purchase and install a new one. Testing a fuse to see if it is actually blown is a very simple task, requiring a minimum of inexpensive tools, and can save both money and time.
A fuse is basically a small piece of wire inside a special housing that is designed to burn in half when an electrical overload is present. All we have to do is determine if that wire is still intact. Some fuses have a small window where the wire can be seen but the view is generally poor, the wire is often very small and mistakes can be made. A 30 second test is foolproof and will tell the tale with no possibility of error.

At it simplest, a fuse tester is nothing more that a a device to check for continuity. It may be in the form of a multimeter, a continuity tester, or a dedicated fuse tester.
In all cases, though, the idea is to send a small current through the fuse; if it passes through the fuse the fuse is good. If it does not the fuse is blown and needs replacement. This means that a battery is necessary to provide that small current and every fuse tester will have a battery in it.
If a tester shows that a fuse is blown, the next step is to check the tester. This is accomplished by touching the test leads together or, in the case of testers without leads, to put a piece of metal (wire, coin, dinner spoon, anything metal) across the probes. If it does not indicate "good" the battery probably needs replacing.