Air Conditioning - A/C Blower won't shut off

Today I came home and the fan in the attic unit of my split-system was on and blowing cold air out of the registers. Being that it is 35-40 degrees outside and I have hot water radiators I am not sure why this was happening. Note that the digital thermostat was set to off and that didn't seem to matter. I was playing with the 4 wires and it still didn't shut off. I had to turn the 60A breaker on the unit off to shut off the fan. When I went outside the condenser wasn't on but can't say it hadn't been. Any help would be greatly appreciated.

Thanks.

Disclaimer: I really have no idea how this whole system works.

is the fan switch on or off?

Just what all do you have up in the attic there? You said 4 wires. Just a AC unit there would only use or need 3

Thanks for the quick response(s). In the attic is a Trane air handler (the only reason I know is because I just found the installation guide). The thermostat is digital and the fan switch is set to auto (as opposed to on) but power is set to off. The 4 wires are yellow, green, orange, and red. The orange and red are both connected to the RC terminal on the thermostat. I removed the thermostat, disconnected the green wire and still the fan stays on. I even tried removing the green wire on the unit thinking it may have shorted somehow w/in the wire between the two. Since my last post I noticed I lost power during the day so I am thinking there could be damage on the fan relay on the unit. Once I get a meter I am going to test the Green screw on the unit and see if I see voltage across it. Any suggestions? Could something have been fried. Haven't noticed any other electronics with issues, just a bunch of blinking clocks.