Well, I'm not sure this was a good idea. I had a 10 amp fuse in line with the battery, and should have taken note when I kept blowing those. It's a motor, so logically the starting current is going to be much more than the running current. A slow blow fuse would have been ideal, maybe 15 amp at that. Anyways, I decided to see how the charging system would handle the lights and fan at the same time.
Worked fine for a little while, I had a voltage meter hooked up and the regulator was compensating. Then suddenly the voltage dropped right down. My regulator was really hot, much warmer than it's ever been. I also lost all power in the system, and the starter wouldn't kick back in.
I checked the 15 amp main fuse, and it had blown open. I replaced it with a 15, turned the ignition on, turned the lights on and after half a second of dim orange glowing, the fuse blew again. Tried it with a 20 amp one, blew again.
At this point, I thought for sure my regulator had shorted out to ground internally, so I removed it and replaced the fuse again. This time, the lights came up and the fuse didn't blow. I reconnected the regulator... and the fuse didn't blow. I reinstalled it onto the frame, didn't blow.
I pulled all the relays and connecters apart, cleaned them with contact cleaner, filled the pins with dielectric grease, and noticed one of the wires had been rubbing on the frame. I taped it up, reinstalled everything, and it was fine again.
I'm not exactly sure what happened. Maybe it was a coincidence that that bare wire had finally shorted out right when I installed the fan. Maybe the fan really does draw too much, and damaged the regulator. But temporarily? I can't be sure, but I'll definitely be searching for a less powerful fan. Unfortunately.
Anyways, that's a heads up for anyone else considering this idea.