Hello Maybe you answered your own question you said you have rodent chit under hood.Did they get into car and nest in upper dash area where the air mix flap is to control temp and chewed some Wires.
Did you say you installed that updated Aux Fan harness or you just changed fuse?Its got a heavy supply wire so you can run a 40 amp fuse.
The one doc for lack of a/c or heat is Af83.40p3400a,If you have contriol unit part #s 163 820 25 89 or 28 89 or 42 89 or 43 89 it may not be controlling air mixing flap correctly.there is vin #s involved but you said cars gone! Tim