Fusible links

If you have fusible links that are wires, tug on them. If they act like a wire, they're good. If they act like a rubber band, they're burned open. Once the cause of the overload is found and repaired, these wires can be spliced and soldered as long as part of that wire is still there to act as the fuse. It is smaller in diameter than the rest of that circuit's wire so it's the weak link in the chain, and the insulation is designed to not burn.

Newer cars have giant plug-in or bolt-in fuses that are still referred to as fuse links. Usually you can tell if they're blown by looking at them, otherwise you can measure their resistance with an ohm meter.