Heater Switch Issues

[toolboxchev]

So I feel like a dumby on this one. First images shows a highlighted area. Its marked as Air Cond 25 amp. Does the heater run off this also if I have no AC?

Or do I put a 10 amp fuse in this location???

Or in the second photo, does the actual heater run off a 3 amp fuse? In the location under the AC circuit.

I keep blowing the heater switch, most likely in high position and the wiring harness. My electrical is all jacked up due to water intrusion, missing markings on my panel in the truck.

Thanks in advance.