Weird sound I never heard before?

2001 MAZDA PROTEGE
50,500 MILES • AUTOMATIC
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LY8178
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Just got home from work, car in park in driveway and turned my A/C and headlights off, opened door and started hearing this weird whirring noise. Sounded like it was coming from the lower front of car under hood driver's side. Turned off the car, opened the hood, and turned back on to see if I could figure out where that sound was coming from but did not come back.

Alternator, battery, and power steering recently checked and in good condition.

Also, the car has been driving fine. No warning lights, smells, rough idle etc.
May 15, 2025 at 6:00 AM
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STRAILER
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Does this car have ABS? If so, I would unplug the fuse for the ABS system which is under the hood on the left side fuse panel (60 amp). If the noise stops then the ABS module will need to be replaced because the relay is stuck on. Please let me know, also can you please try to upload the video of the noise again?
May 16, 2025 at 11:15 AM
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LY8178
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Thank you for the reply. No, my car does not have ABS, it's a LX 2.0

Also, the sound stopped after I turned the car off and restarted. It started initially when I was parked in my driveway then opened a backseat door to put up my rear sunshade, that's when it first started.

I haven't driven anywhere since but started up the car a few times and tried opening the same backseat door and the sound never returned.

Could it be my anti-theft system glitching? It was installed in 2001 when I got the car, and the sound is like a periodic weak horn.

Going to try to re-upload the video, let me know if it works!

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May 16, 2025 at 6:21 PM
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LY8178
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Converted clip to mp4 to see if that works.
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May 16, 2025 at 8:34 PM
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STRAILER
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Yep, that worked. Is there a chance you can open the hood when the noise is happening to see if you can find what is making the noise? It sounds like a controller is going bad, let's run the codes to see if any codes are stored.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

I noticed the engine was running during the noise, does it do the same thing with the engine off? Please go over this guide and get back to us.

May 18, 2025 at 5:40 PM
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LY8178
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The sound does stop when the engine is off.

I drove a few times and did not hear it again until I turned off the ac this morning, then it returned. I turned the A/C back on and it was louder and more constant. Turned it off and stopped. Toggling it sometimes there as that sound, other times no sound.

I popped the hood to see if I could track the location of the sound but then it stopped making the sound completely.

Car has been driving fine and no warning or check engine lights. Unfortunately I do not have a code reader.

I am guessing it is my A/C clutch going bad?
May 19, 2025 at 3:52 AM
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STRAILER
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Ahh, the clue, it seems like the A/C is a tad low on refrigerant. That will make the clutch cycle like that, this video will show you how to add to the A/C system.

https://www.youtube.com/watch?v=4UjfQKvrB6Y

Please go over this guide and get back to us.
May 19, 2025 at 9:53 AM