Whistle sound

When I accelerate I get a strange whistling sound. It sounds like someone is blowing across an old fire alarm bell. Kind of a ringing sound. I barely heard it when I first got the car and now it's louder? Is this normal?
Edit: I'm trying to get the sound recorded but go figure it hasn't made the noise lately. When I first got the car I only heard it right at the very second I accelerated from the stop. Now it goes on for a few seconds after I accelerate from a stop or when I accelerate while the car is moving.

nanotube said:

When I accelerate I get a strange whistling sound coming from the CVT. It sounds like someone is blowing across an old fire alarm bell. Kind of a ringing sound. I barely heard it when I first got the car and now it's louder? Is this normal? I heard people mentioning a whining sound but not a metallic whistling sound. I don't have a tuner on this car yet.

Click to expand...

There is a turbo whistling sound that's normal, I hear it all the time. You can always have the dealership check it out if it's something else.

My friend driving my car thought it there was a police siren every time he accelerated. Didnt start hearing this noise until ktunder stage 2 flash or engine break in

It's much louder when it's colder out.

I finally got a couple of videos of the noise. Originally I thought it might be the CVT but it maybe different so I changed the title. The funny thing is that it stops when I turn the fan off to the heat/ac unit. It does not make this noise while stopped, only when I accelerate and doesn't do it every time.

nanotube said:

I finally got a couple of videos of the noise. Originally I thought it might be the CVT but it maybe different so I changed the title. The funny thing is that it stops when I turn the fan off to the heat/ac unit. It does not make this noise while stopped, only when I accelerate and doesn't do it every time.

Click to expand...

I have the same issue. It may be the compressor motor from what I have read. Like you, I don't hear the noise when I turn the heater/ac blower off.

Based on the similar threads below and your response, sounds like it's the AC and nothing to worry about. Kind of strange since I never heard this sound before in any other car I owned and that includes several Honda's and Acura's. Thanks.

nanotube said:

When I accelerate I get a strange whistling sound. It sounds like someone is blowing across an old fire alarm bell. Kind of a ringing sound. I barely heard it when I first got the car and now it's louder? Is this normal?
Edit: I'm trying to get the sound recorded but go figure it hasn't made the noise lately. When I first got the car I only heard it right at the very second I accelerated from the stop. Now it goes on for a few seconds after I accelerate from a stop or when I accelerate while the car is moving.

Click to expand...

Lol that’s funny. I happened to notice that today in my car. Definitely AC

This has happened to me too on my new 2018 Civic Sport (CVT). Exact same noise from the video. I didn't realize it was the AC but once I turned the AC off the noise stopped. It is much louder in sport mode at low speeds. When I am in regular drive, I rarely hear the noise. I'll get the dealer to look at it when I go in for my first oil change but good to know it's not just me.

Anyone get this issue fixed? I seem to be having it too, guessing it might be the HVAC fan motor because it stops when I turn it off.

2017 civic Si - same thing. Drove me nuts as I couldn't figure it out until I turned hvac unit off. Definitely A/C. Wtf.

Any update to this problem? Having the same sound on my 17 sport hatch.

Apologies in advance for the long post...

I've been noticing the whistling noise heard in the videos posted by @nanotube for a while now and have been trying to determine the cause, these types of noises drive me insane until I can find out what's going on. I came across this thread at work and wanted to share what I've found so far.

I build computers in my spare time and initially identified the noise as identical to the sound of old PC fans with bad bearings leading me to believe that the blower motor was to blame. However, I did some further testing which made me second guess this.

I've found that the whistling noise does not seem to be affected by fan speed or engine RPM. On the contrary, the noise is most prominent when completely stopped and the fan is on the lowest setting (less ambient noise to drown it out). Whistling noise is is intermittent but seems to be on a 'cycle' of sorts, it will be present for several seconds then stop for several seconds. Whistling noise stops completely when the fan is turned off. Whistling noise also stops completely when the engine is turned off but the fan is left running. At this point I'm thinking the air compressor may be to blame. I'm not as inclined as some when it comes to cars but as I understand it the air compressor is the only part of the HVAC system that requires the engine to be running.

I asked my local dealer to investigate when I took the car in for routine maintenance last week. I sat in the car with the tech and he said the noise was due to the configuration of the HVAC system in the newer Civics. Previous Hondas have used a dual radiator fan configuration with one fan for low speed and one for high. Newer Civics use a single fan configuration and when the fan RPM is increased it creates a noticeable 'turbine' sound. The Honda tech suspects Honda went with a single fan configuration to save space, possibly to make room for the intercooler. This being said, I have heard the 'turbine' noise and it is definitely not the same as the 'whistling' noise.

Flash forward to today when I searched the forums here and found several posts on the HVAC system in general. I did some additional testing this evening after leaving work and believe I may have found the cause but I'd be interested to see if this applies to others who are experiencing the same noise.

I don't normally run my A/C even in warm weather so I decided to test the A/C issue reported in another thread (here) to see if it was related. I ran my A/C while driving home and noticed that a new 'A/C ON' icon appeared on the climate control display (pictured below). Now that I think about it, I don't think I'd ever turned A/C on in my car...

Noise Present


When I got home I sat for a moment and confirmed that the whistling noise was still present with A/C on. I switched A/C off and the whistling noise immediately stopped, even though all other climate settings remained the same and were consistent with settings used to reproduce the whistling noise previously. At this point I'm still leaning towards air compressor.

No Noise


I also found that you can remove the A/C On/Off icons by switching to 'Auto' and then making manual adjustments to other settings. However, switching to Auto to remove the A/C On/Off icon and then manually setting everything else to the way it was before results in the noise being present again.

Noise Present Again



This has led me to believe that only the individual climate settings modified by the user will change after using Auto. Leaving the air configured as seen in image 3 seems to leave the air compressor in 'Auto' mode which, apparently, will default to always on even when the temperature specified does not require it. I went through the above process a few times and was successfully able to trigger the whistling noise and then stop it by switching A/C to Off.

Can some of you who are experiencing this issue perform this test to see if you are also able to stop the noise? Unfortunately, the whistling noise may be expected behavior while the air compressor is running but it'd be nice to at least know why this is happening.

My current theory is that what we are hearing is the evaporator pulsing/humming to the Freon that's being pulse compressed from the vanes of the scrolling compressor. My hope is that maybe we could figure out how to get to the evaporator and that we could then shim/wrap what ever part of it that is vibrating.

I am not sure if you guys are still having this issue. I took delivery of a 2018 Civic Hatchback, I had this issue two days after. I just took it in, they are replacing the whole A/C unit for me, however, parts are on backorder so they gave me a rental.