03 Gt Fan Fuse Keeps Blowing Instantly???

I'm a big believer in occam's razor.

https://en.wikipedia.org/wiki/Occam's_razor

Well........Given the parts that you have replaced Occam's Razor would say that your problem HAS to be a wiring harness fault. Likely a short to ground somewhere in the wiring harness. Given that the fuse does not blow until the motor is started, the fault is most likely between the CCRM and the fan.

Do you have a Volt-Ohm meter (VOM)? If so, disconnect the fan's electrical connector. Measure the key off resistance from the body side fan connector back to battery negative. Be sure to zero the meter before testing. Post the results. For the black wire the resistance should be low. For the other two wires the resistance should be very high.

When looking for a wiring harness fault it's also very effective to perform a visual inspection of the wiring harness. Look for any evidence of physical (or rodent activity) damage to the harness.

I'm also assuming that you have inspected the fan connector itself looking for evidence of over heating.

The other possibility is a "modification" done to the car. Tell us about any "special" modifications done to this car. Big radio? Headlights?