Electrical Help Please

I also think it will be really helpful to figure out the battery and new circuits have been connected into the original system.

All I have to go from is the photos posted.
It looks like power for the fans comes from a connection by the firewall or inside or ?


It looks like there may be three wires on the relay stud?
Guessing
One heavy ga from the battery
Second heavy gage either to the starter (which could be a problem) or to feed relays or an auxilery fusebox or such.
Third may be the original connection to the main junction via the ammeter.