2003 mustang gt keeps blowing 50 amp cooling fan fuse

Looking at the electrical manual, I can see the power is fed by a 50 amp fuse at the Battery Junction Box, and a 30 amp fuse in the High Current Fuse Panel. Also, I'm quoting "PCM determines when fan operation is required by monitoring coolant temperature, vehicle speed and a/c status. When operation is required, PCM signals CCRM to turn on fan to desired speed." PCM is Powertrain Control Module, located behind RF passenger kick panel. CCRM is Constant Control Relay Module, located in engine compartment, right fender by air cleaner housing. I can't see how either module would be blowing a fuse, so it's got to be the fan motor itself (which you've already replaced), or a short in a feed wire to the fan. There's 2 wires feeding the fan, Orange/light blue stripe coming from CCRM, and a Red/orange stripe, coming from the High Current Fuse Panel. Trace those wires back from the fan and look for a problem. There are connectors along the way. Hope this helps you get in the right direction to trouble shoot. The black wire at the fan is Ground.

+1 on on above.

In addition, confirm that the cooling fan runs on low speed with the AC on. Start it and let it idle in the driveway with the AC on. The low speed fan should run all of the time. Allow it to run until the motor gets hot enough to call for the High Speed fan. What would help to know is if that is when the fuse blows.

However, I have to believe that if the fan is new and is not binding, there is a wiring fault somewhere.