pretty sure its not the blower motor. noise sounds like its coming from pulleys in the engine bay
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2005 Dodge Ram 1500 Question: rattling/vibration noise coming from the engine compartment when ac is on??
Answer #1Carmasters Automotive LLC (47 Answers) , Virginia Beach, VA - (757) 793-2234carmaster July 08, 2013, 05:09Technician
That could be your A/C Compressor or and component on your serpentine belt drive system such as pulley bearings in tensioner, idler, alternator for example. When the A/C compressor engages it increases load on the belt which is why it could be another component. Best to listen to each component with a stethoscope with engine running and A/C compressor clutch engaged, then to confirm remove the belt, start engine briefly to make sure noise is gone and not internal, shut off engine. If noise is gone then with engine shut off, spin each pulley driven by the belt by hand while listening with stethoscope to confirm source of noise heard when belt was on and engine was running (noise/sound travels so well through metal that can be fooled sometimes as well can have more than one bearing failing but the one that is the loudest can mask the not as bad failing bearing noise). If need checked out or repaired please call Michael or Josh at 757-4456-0722 thanks, Jim