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Originally Posted by 71CHEVYSHORTBED402
Great info. thank you. Let me ask, what's the difference between a fusible link and an in-line fuse? One reason I ask is I have two other whatUcallits described below. These units are rubber boot insulated and pull apart. In fact, I pulled one apart and it sounded like I may have broken the gizmo inside. No harm done, I'm getting new wires. If needed I'll add pictures.
One rubber boot dude for the black wire from the firewall block to the junction block. The unit is near the junction block.
One rubber boot dude for the black & white striped wire from the firewall block. The end of this wire is soldered where the cluster of red wires are soldered as described in post one. The unit is near where it's soldered.
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You're welcome! A fusible link is basically just a short section of smaller gauge wire that (in the event of a short to ground or major overload) will act as a fuse to protect the rest of the wire in the circuit from melting. The fusible link wire has special insulation that is designed to stay intact even when the wire inside burns out. So a quick & easy way to test a fusible link is to give it a gentle tug to see if it feels stretchy (if it does, the wire inside is burned out). The insulation will often partially melt and give off lots of smoke when a fusible link burns out so they should never be used inside the passenger compartment of a vehicle.
One of the biggest differences between a fusible link and an inline fuse is that a fusible link acts like a really slow blow fuse. In other words a fusible link will stand up to short term overloads but still offer protection in the event of a major problem. That can be an advantage in situations where you don't want a fuse to blow due to a temporary surge in current (such as when an electric motor is started). Fusible links also tend to be a bit more compact than a fuse in an inline holder (especially for larger sizes). And not having a fuse holder cuts down on potential loose contact & corrosion issues.
Those two black rubber boot things you found are inline fuse holders that hold the fuses that protect the ammeter (battery gauge) circuit. They use SFE-4 fuses and replacements are still readily available if you broke one. This application uses fuses instead of fusible links since the current is so small. A fusible link wire small enough to burn out at 4 amps would be way too tiny and delicate to be practical.