What fuse is considered always on in 1984 Chevy s10 truck?

In a 1984 Chevy S10, the fuse that's always "hot" (meaning it receives power even with the ignition off) is typically the fuse for the battery feed. This is often labeled something like "BATTERY" or "BAT". It's sometimes a larger amperage fuse than the others.

However, there's no single definitive answer without checking your specific truck's fuse box diagram. The location and exact labeling can vary slightly depending on options and trim level. Consult your owner's manual or a wiring diagram for your specific year and model for certainty. The fuse box cover often has a diagram printed on it as well.