A/C fuse blows when key is turned on

then you have a short in the power wire leading to HVAC or wherever else fuse powers up. it is a brown wire under dash if something has been added to dash like a switch/light etc. then look for a screw contacting harness as it may have screwed into it.

Okay i understand. Tell me: where would this wire come from? And how does that work? The battery cable goes to what? The "brain"? Then splits into many wires? Then goes wherever they need to? So do you recommend starting at fuse panel? I would think but?

this leads from the ign3/hvac fuse then to a splice pak then to all actuators. unplug actuators one at a time in pic and see if fuse blows if not it may just be a bad actuator. I am assuming this is a manual a/c system and not auto temp where you set temperature. If you need another answer immediately I will be available Saturday to answer this. I doubt it is from the splice or fuse panel unless it's a loose connection.