The manufacturer may instead just basically ignore you, even if you mention (or threaten) that you will be calling the CPSC. If you feel strongly about it (as in, you are pretty sure this isn't your fault somehow), go ahead and then call the CPSC and report it. You can then reasonably expect to hear back from the company, and maybe get your replacement fan (or at least blades) for free.
Short personal story: This has been my experience, especially when safety is involved. Sharp customer service repeatedly ignored our pleas to fix or even help explain a microwave gone berzerk (heating with door open). I felt pretty strongly (my 2yr old was standing right infront of the door when I opened it!), so called the CPSC. I quickly got a followup call from "Marcy", who clearly knew what was what, and treated me with courtesy and respect. She arranged a repair, then when that turned up nothing, got an engineer at Sharp to explain what was going on, then followed up a few weeks later and then again a few months later just to make sure I was still a happy customer.
PS -- the "microwave on with door open" turned out to be a false alarm in this case. If one of the redundant door switches fails (e.g, one says "closed" and other says "open"), then the microwave (this one, at least) shuts of the microwave element but powers up the rest of the cycle (fan on, light on, turntable on). The engineer explained that this is their cute idea of a hard-to-ignore warning, as it should scare any reasonable consumer into getting an immediate repair. Sure as hell scared me -- its just totally unexpected to have the microwave seem power up when your hand is inside!
-Kevin