This 1994 Chevrolet C3500 came in with a ton of problems. In the process of wrapping things up I wanted to show how to replace a damaged fusible link.
First of all so many people think that the white (sometimes black) plastic piece is the fusible link. It is not. The fusible link is the special grade of undersized wire that is installed between the ring terminal and the main wire just below the white plastic piece. The white plastic piece has two purposes: insulate the splice connection and identify the size of the fusible link wire.
This one has the number 16 on it, indicating that 16 gauge fusible link wire is used. Notice that someone had previously made a repair to the damaged fusible link by simply splicing the two burnt pieces back together. This changes the load rating of what fusible link is left and will cause the harness to burn if a short reoccurs.
Fusible link wire is special in that the copper wire inside is designed to melt if overloaded. Also the insulation is not supposed to catch fire when the fusible link melts from a short on its protected circuit.
The first step is to cut the whole fusible link assembly off of the main wire.
The new piece of fusible link need to be cut to six inches in length. There are special step down splicing terminals that hardly anyone ever has in stock. To work around this I select a terminal that will properly fit the wire that is to be protected. I then insert the fusible link wire into that terminal to gauge how big of a void needs to be filled.
I then strip off more than enough insulation so that I have enough wire to shape into filler for the larger terminal.
In this particular case it was folded four times.
Then rolled into a tight bundle.
That tight bundle is crimped into the terminal.
The same thing is done with the appropriate ring terminal. I choose to use the same gauge sized ring terminal as was used to connect to the protected circuit. The lighter gauge ring terminal that would fit the size of the original unfolded fusible link wire would be too flimsy to properly carry both the electrical load of the circuit and the weight. Also the lighter terminal can be damaged just by tightening the attaching nut. These are techniques that I have developed over many years of observation of what works and what does not.
I install heat shrink tubing on both the splice terminal and the ring terminal.
The fusible link is now properly repaired.