Rep Power: 0

I have a new to me 2012 civic sedan. There is a noise only when blower is and turned up high (Not noticeable with fan on low side) and on heat. Another words the noise is apparent only when blower is on high and the climate control selector is on heat. If you rotate the temperature from cold to hot the blower noise goes away on cold. Which vent, heater, or defrost selected does not matter loud sound on heat.. Sounds like blower has loud vibration or debris flapping. But strangely only on hot not cold or AC. When car warms to hot and after some time the noise often goes away, but returns again when cold or always first starting. I have dropped blower checked and cleaned out cabin air. That's not issue. Especially if no noise is only there when calling for heat and engine is cold. Will stop if rotated to cold AC or not.