My 2009 LS460 is making a repeated whirring noise which is particularly noticeable when stopped or at low speeds only after switching on the A/C. Also the rpm moves ever so slightly in sync with the noise especially at idle.Sound goes if i switch the A/C off. Found another post with the same issue on a gs460 and i have attached the YouTube clip that user had attached.

 

does anyone know the reason behind this noise? I am worried its the ac compressor kicking on and off and might damage it

 

Tough to say the exact cause. Do you hear a similar rhythm under the hood?

 

no i along with my local ac tech checked the belts and compressor but no such noise under the hood. can only be heard from inside. but he did mention it seems the compressor is constantly varying pressure after checking it which might explain the constant change in rhythm of the rpm
the car has a fault stored in history related to the servomotor circuit for the air inlet and outlet damper control in the front

 

Might be on to something, try to duplicate the noise with A/C off by changing modes and fan speed. Or it could be the cycling noise will only happen with the A/C on due to a bad servo.

 

will definitely look into that. thanks

 

I used compressed air to blow out mine. Dang Squirrels

 

my mechanic had recently cleaned the cabin air filter compartment using pressurised air when changing the air filter but the sound still persists

 

Make sure the cover for the cabin filter is in place correctly.

 

Any update? I am having the same issue and can't figure out how to fix it.

 

no luck with the sound. checked cabin filter and other things mentioned here but no luck. my ac tech said there was a slight variation in compressor pressure in tune with the sound but could not find the reason. let me know if you are able to figure it out

 

Any update to this thread? Mine is doing the same exact thing.

 

Yeah, still no luck with that. The ac works pretty well so just stopped bothering about it

 

Thanks for responding back! Out of curiosity, have you checked the pressure in your ac lines? Could this be caused by them being over or under pressured?

 

I have this on my 2017 LS460, same symptoms (i.e., whirring only happens when A/C is on and goes away the minute I turn off the A/C). After hours of looking into it, I've come to the tentative conclusion that it is an engine noise. in other words, the ever so small tax that the A/C puts on the engine causes the engine to make the whirring noise. Let me explain.

I opened up my glove compartment and removed the cabin air filter, exposing the A/C fan. I ran my car with the A/C fan exposed for about 15 minutes until the noise started with the A/C. Putting my ear right up to the open A/C fan, the fan itself was silent. Zero noise from the fan. Turn off A/C and the whirring noise goes away. Turn on A/C, whirring starts. but no noise at all from the A/C fan.

I open up the hood and repeat the process. Can't hear the whirring in the engine bay because it's too loud. When I turn the A/C on, the noise in the engine bay slightly changes. I think this slight change produces the whirring sound inside the cabin.

That's all I got. but I think that's what's happening.

Any other thoughts?