We have a ICP GNE100F14A1 furnace and it has started making a rattling noise which becomes a whine at regular speed. On inspection it seems that some blades of the rotor (fan blades) visible from the front are sticking at some point in the rotation. How to fix this?

Plastic blades? Heat distorts them sometimes. They also get loose on the shaft. . Replace the fan rotor assembly after making sure the motor bearing isn't worn.

The main blades are not plastc. I was able to stop the noise by bending the blades that touched the housing. However, I also found that the black plastic rotor that is simply pushed on the end of the motor shaft (seems to be there to cool the motor) is broken where the shaft is attached. This part does not seem to be available on its own too. And to make matters worse, the local hvac outfits don't wan t to sell any parts.