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Loud rattling noise coming from engine compartment when AC is turned on

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Pete5605, Nov 4, 2024.

  1. Pete5605

    Pete5605 New Member

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    I could really use some help with this when I'm stumped. About 3 weeks ago I've noticed when I turn the AC on there's a loud rattling noise coming from the front end. I jumped the gun and immediately assumed it was the compressor. I've replaced the compressor and the condenser. I've recharged the system and the AC was working great. The problem is the noise is still there. There is no trouble codes. Car runs great otherwise. As soon as AC button is pushed the compressor comes on and I have AC but I have a very loud rattling sound near the right front of the engine compartment? Any help would be greatly appreciated.
     
  2. JC91006

    JC91006 Senior Member

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    You can turn on the AC and walk to the front of you car to see what the noise is. It could be a loose fan housing, missing some clips/bolts.
     
    Brian1954 likes this.
  3. Tombukt2

    Tombukt2 Senior Member

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    If you step on the gas a little bit does the rattling stop and everything sound normal I don't mean floor it Just bring the idle off and everything cleans up?
     
  4. Pete5605

    Pete5605 New Member

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    Three
    Car motor is running good. As soon as I press the AC button I get a severe rattling noise. If I stand in front of the engine the noise appears to be coming from just right of the air cleaner box. There is nothing loose or rattling that can be seen. When I step on the gas and give it a little gas the noise does not go away. I just don't understand why this happens when I turn the AC on? I have replaced the AC in the condenser because I thought the AC compressor was bad but it was not. Evacuated the system after the parts were changed and recharged per OEM instructions AC works great but bad rattling is still there? Help! I am not a Toyota technician. I have worked for general motors for many years years ago but I'm not familiar with these systems on these hybrids that well
     
  5. Pete5605

    Pete5605 New Member

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    Thank you everybody for your help. Just turned out to be a rather simple problem. Every time I turn the AC on I would hear what to me sounded like bearings that went bad like a rattle. This time I shut the AC off and when the fan came on with the AC off for cooling the noise came back. Using a stethoscope a trouble shot it to being the bearings in the fan. I did not even consider this since I replaced that fan about a year ago. Thanks for your help everybody
     
    Brian1954 and bisco like this.
  6. Tombukt2

    Tombukt2 Senior Member

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    Yeah cheap aftermarket fan motors 10 do exactly this so there you go Good you got it sorted now maybe by the $40 fan motor instead of the $28 one or something along those lines I generally try to pick middle of the road pricing and parts manufacturing generally I don't need the $300 original part but I don't want to $28 fake part so somewhere around a $60 made by a major manufacturer preferably or something like that you know that kind of thing.