|It is extremely important to understand that if a fuse looks good, it might not in fact be good! Fuses can appear to be fine and have a break in them so small that it cannot be seen by the naked eye!
Therefore it is important to check a fuse with an Ohmmeter or a continuity tester instead of assuming that it is good. A significant percentage of all circuit boards are “dead” have nothing wrong with them other than a blown fuse. Assumptions can waste a lot of time! The fuse shown below looks perfectly good, but is open under one of the end caps!|
|Use a multimeter and set the range switch to the lowest resistance range to check the fuse. A good fuse will read 0 ohms (depending on what the meter reads when the leads are held together) and a bad fuse will read the same as holding the leads in the air.
The illustrations below show how to test fuses, showing each fuse as good. There is no gray area, the fuse is either good or it is not.|
Testing a standard fuse
Testing an automotive style fuse
|You can also use a “battery operated continuity tester” as shown in the illustration below (also indicating a good fuse)*Important note: A standard test light without the built-in battery will not work! It must have a battery built-in to make the lamp light up!|