As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FAN WHEEL DISINTEGRATED - ONLY END PLATE LEFT. ALL VANES GONE. MULTIPLE FAILURES OF THESE UNITS RECENTLY. SUBMITTER STATED APPEARS TO BE CAUSED BY IMBALANCE. FAN WHEELS USED TO COME WITH METAL BALANCE - CLIPS ON VANES. NO LONGER COME THAT WAY. SOME VIBRATE SO BADLY THAT COMBUSTION BLOWER MOTORS HAVE BEEN DESTROYED.