When I restored my fresh air heater I tried to fix the centre hub on the fan and thought it would be okay but I could not get the fan to balance and it would wobble . These fans are different and it may work .I don’t know what you paid for your fan motor but you could most likely find one at your local flaps that is the same except for the smaller shaft size .Might be worth it to take the motor and fan down to see if they have one then you could return the one with the bigger shaft.
