To remove a fuse:
- With glass cartridge or blade-type fuses, a special fuse removing tool can be used to remove a bad fuse.
- Blade-type fuses are easy to remove by hand or with a needle nose pliers.
To replace a fuse:
- Be sure to replace a fuse with the correct one for the application.
- SFE (Society of Fuse Engineers) and all-glass cartridge (sometimes called "Bussman" or "Buss") fuses will interchange with one another, so care is required.
- Be sure that the fuse is the correct rating. Too low an amp rating will result in burned fuses. Too high a rating can cause a fire.
- Check the end of the fuse for its amp rating. The correct amp rating of the fuse to be used is listed on the fuse block.
- Fuses are generally numbered, and the main components abbreviated.
Typical fuse box or panel.
- On late-model cars, there may be icons or symbols indicating which circuits they serve. This identification system is covered in more detail in the owner's and service manuals.
To calculate the correct fuse rating, use Watt's law: watts ÷ volts = amperes. For example, if you are installing a pair of 55-watt fog lights, divide 55 by the battery voltage (12 volts) to find out how much current the circuit has to carry. Since 55 ÷ 12 = 4.58, the current is approximately 5 amperes. To allow for current surges, the correct in-line fuse should be rated slightly higher than the normal current flow. In this case, an 8- or 10-ampere fuse would do the job.
It's advisable to carry an assortment of spare fuses in the glove compartment. It is difficult to know when one will blow. Also, you should learn borrow a fuse from a less critical circuit. For example, it is possible to do without power for the radio or air conditioner, if a fuse is needed for the headlights or brake lights. Make certain, however, that the fuse borrowed and later replaced has the same current rating. Remember that a blown fuse was caused by something going wrong. Replacing the fuse may or may not give a temporary solution to the problem.