There are three basic types of fuses in automotive use: blade, ceramic, and cartridge.
Blade fuse, ceramic fuse, and cartridge fuse.
Occasional fuse failure can be due to a defective fuse. Corrosion on the end of the fuse can cause failure too.
The cartridge fuse is found on most older domestic cars and a few imports. To check this type of fuse, look for a break in the internal metal strip. Discoloration of the glass cover or glue bubbling around the metal end caps is an indication of overheating.
Late-model domestic vehicles and many imports use blade or spade fuses. To check the fuse, pull it from the fuse panel and look at the fuse element through the transparent plastic housing. Look for internal breaks and discoloration.
The ceramic fuse is used on many European imports. The core is a ceramic insulator with a conductive metal strip along one side. To check this type of fuse, look for a break in the contact strip on the outside of the fuse.
A visual check of the fuses in questions can sometimes show a burned fuse. Sometimes, a fuse can blow where it cannot be seen.
Test a questionable fuse with an ohmmeter.
All types of fuses can be checked with an ohmmeter or test light. if the fuse is good, there will be continuity through it.
When inspecting fuses, also inspect the fuse link:
- Fuse link wire is covered with insulation that bubbles if a fuse link melts.
- The blisters on the insulation indicate the failure in the fuse link.
- If the insulation appears good, pull lightly on the wire.
- If the link stretches, the wire has melted.
- Of course, when it is hard to determine if the fuse link is burned out, check for continuity through the link with a testlight or ohmmeter.