Brett, can I spin the fan without taking off the back? I managed to rotate the fan a little using a screwdriver through the fan shield. However, it is still throwing the Err64. On powerup, sometimes I hear relays click, sometimes I don't.
If you still have your old power unit, plug it in (somehow?) take the back off where the fan is (or just spin the shaft if it's disconnected from the pump) and see if it works.