So I unplugged the fan and ran a couple of speaker wires from the battery to the plug male prongs. It didn't come on. next I'll let it run a while to warm up then I'm wondering if the wires I'm using are too thin or I don't have a good connection...?It's a hard space to work in with all the other wires and accessories in the way and my big hands..
OK so let me get this straight you found the plug coming from the fan closest to the fan and unplugged it and ran wires from the battery to that plug and the fan never ran ? if so the fan is not working.
The same test could be done simply by just unplugging the fan and using a jump box or even a 12 volt automotive charger and some wire rather than going to that PITA battery box.
I assume the fan can be spun by hand easily with little to no resistance.
Are you in a hot climate and did the fan run a lot normally before this ??? maybe it is just worn out.
even if the fan is broken it should still be getting a signal and power to come on when the temp limit is hit.
I'd hook my volt meter to the vehicle side of the fan plug and run the machine until it gets warm and see if I'm getting 12 volts switched on if not you'll have to go back further to find the problem, control, temp sensor, maybe wiring.
At some point that wire will have to have 12 volts switched on to run the fan and you want to make sure that is working as well, if it does get 12 volts then get a new fan.A bad thermostat will cause it to overheat but the fan should still come on if it is working.
my fan ran after a short run around the yard doing some work with only two squares on the temp gauge and temp outside was around 77F at the time.