As I recall, I ended up having to replace the heater core (and purchase new O-rings and coolant, of course). The fans were working but blowing cool/cold air, and causing the inside of the windshield to fog up! By that point, coolant had leaked inside the car pretty much ruining the sponge/noise reduction layer under the carpet
That was my first experience with heater cores, and hopefully the last!
Not sure if this helps but do wish you good luck with your repairs!