14 Gauge Fusible Link

  5 1/2 “ to 6” long           

Notice in the table above that there is always a four number size difference between the Fusible Link wire gauge size, and the size of wire going out to the rest of the circuit.  (And with wire gauge sizes, the larger number is for a smaller diameter–as with shotgun barrels, the 20 gauge bore diameter is smaller than the 12 gauge bore diameter.)

The four number differences in gauge size will create the correctly calibrated bottleneck for the Fusible Link to function.  Normal amounts of current flow through the Fusible Link do not generate enough heat to warm it up, and normal amount of current flow does not result with significant voltage drop.  But in the event of a “full-overload” (“short-to-ground”) problem, excessive current flow through the Fusible Link (bottle-neck effect) will overheat the Fusible Link and burn it out.  The protected circuit will be automatically disconnected from power.

Installation and function of a Fusible Link is similar to the “cartridge type,” in-line fuse.  But the Fusible Link does not deteriorate or have meltdown problems with constant use in heavy-duty systems, as the cartridge type fuse is famous for.  (Chevy began installing Fusible Link wires in the main-power circuits with ’66 models, and of those old cars that are still in use, most of the original Fusible Link wires are still in place.  If a Fusible Link burned out then it saved the car!)

Examples of circuits where the Fusible Link wire will be the most reliable short-circuit protection are; *the main power wire to the dash area, *the alternator-to-battery “charging wire,” *power-up wire to electric radiator fans, and other systems where the amount of current flow is a large amount for long periods of time.

NOTES about Fusible Links  Only a serious short will cause a Fusible Link to burn–it disconnects a circuit from power just before the rest of the wiring in a circuit would be damaged.  Momentary overloads will not burn out a Fusible Link–such as arcing a wrench between ground and an exposed terminal.

The insulation of the Fusible Link wire is soft and non-flammable, sometimes the conductor strands within will burn without noticeable damage to the insulation.  A good test is to try stretching it.  If it stretches like a rubber band then the wire within has burned out.

Keep them out of the cockpit!  (When Fusible Links burn they often emit sparks and smoke.)

When installing the Fusible Links, the wire terminals should be crimped, then soldered, and then insulated with shrinkable tubing.  (An on-board spare may be installed too.) 

Learn more about Fusible Link wires in the “tech is made simple” book, from M.A.D.