The best substitution fuse is a fuse with the same current and time delay ratings and a higher
If a lower current rating or a faster time delay rating is used, the fuse may open under normal
Substitute fuses must have the same style (physical dimensions) as the specified fuse.
Proper Fit of Replacement Fuses
When you have obtained a proper replacement fuse, you must make certain it will fit correctly in the
fuseholder. If the fuseholder is corroded, the fuse will not fit properly. In addition, the corrosion can cause
increased resistance or heating. Clean corroded terminals with fine sandpaper so that all corrosion is
removed. Do NOT lubricate the terminals. If the terminals are badly pitted, replace the fuseholder. Be
certain the replacement fuseholder is the correct size and type by checking the parts list in the technical
manual for the equipment.
After you check for and correct any corrosion problems, be certain the fuse fits tightly in the
fuseholder. When you insert the fuse in the cap of a plug-type fuseholder, the fuse should fit tightly. A
small amount of pressure should be needed to insert the fuse and cap into the fuseholder body.
In clip-type fuseholders, the clips can be easily bent out of shape. This causes an incorrect fit, which
in time could cause an equipment malfunction. Figure 2-14 shows examples of correct and incorrect fuse
contacts for clip-type fuseholders used with knifeblade and ferrule cartridge fuses. The clips shown in the
left picture of each row have the correct contact. The three pictures on the right of each row show
incorrect contact. Notice how the clips are not contacting completely with the knifeblade or ferrules. This
incomplete contact can. cause corrosion at the contacts, which in turn can create a high resistance and
drop some of the circuit voltage at this point.
Figure 2-14.Contact between clips and fuses.
If the fuse clips do not make complete contact with the fuse, try to bend the clips back into shape. If
the clips cannot be repaired by bending, replace the fuseholder or use clip clamps. Clip clamps are shown
in figure 2-15.