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Weird air conditioner noise

My 2007 Honda CRV makes an ear-piercing noise, similar to what a dog whistle sounds like when I’m driving at high speeds on the interstate. Some times it’s when I’m driving 40ish mph on a city street with an incline, or an incline on the Interstate. I thought it was my engine, but now I’ve noticed it only happens when the air conditioner is on. When I turn the AC off, the noise stops right away. I took the car back to the dealer, and they checked it out. Even had an employee take it home to test it out on the interstate. They say they heard nothing. But other people have heard it. It’s summer time and the noise has come back. (I didn’t notice it with the heater). So what gives? Do I just have sensitive hearing or is something wrong? I want it fixed while it’s still under warranty!

You may very well have sensitive hearing AND the noise is indicitive of a future problem developing.

Are you young ? It is a known fact that teens can hear high frequencies that middle agers can’t.
Especially me with my noise caused tinitis might not be able to hear your noise during a test drive.
Have a younger tech ride with you on a test drive. When the noise occurs point it out instantly so they can hear any difference right then and there.

If they still elect to repair nothing…GET IT IN WRITING ( your repair order should detail what they did and didn’t do. ) and ‘on the record’ that a diagnosis was attempted and what the concern was. After the warranty is over they could still repair, under warranty, a pre-existing condition that is well documented as such.

Sounds like the expansion valve. I believe there is a TSB on this. I don’t think it leads to any kind of functional problem, just the unpleasant noise.

Why would the expansion valve cause this noise?
In response to the first post - I am younger but I refuse to believe older folks can’t hear the noise. It’s also hard to do a test drive with a mechanic because there’s no guarantee the noise will happen when I turn on the AC - might run out of interstate before it hapens. I have taken it in and documented it, but are they required to honor that after the warranty expires? I’m thinking about recording the noise with a tape recorder.

"Why would the expansion valve cause this noise? "
Why does it make a whistle sound when you blow air through your lips (when lips are positioned correctly)? It’s the same principle with the expansion valve. A fluid is rushing past a restriction.

Most automotive warranties ( Ford experience ) have provisions for covering a repair, after warranty is over, of an intermitent problem that existed while in warranty which then developed into a malfunction. sometime this requires extra paperwork and approvals but it gets done…if provable that it pre-existed. And therein lies the crux…proof.

Many dealers who open a repair order for work that really doesn’t have hours or parts invested in it , will just void out that repair order to simplify their paperwork, effectively erasing that work from the permanent record.

You will want your diagnostics and problem description to be on that permanent repair history which follows your v.i.n. wherever that vehicle goes.
Just having been to the dealer for a problem they couldn’t prove might not give you “pre-existing condition” rights after warranty unless the attempt to diagnose is, in fact, on the record.

I’ve noticed no one really gave you an answer to your question.:0( I am actually having the same problem. I only hear the noise when my car starts up and when the air conditioner is on. I checked my serpentine belt and it has worn down, so that could be my problem. Check your belts. I hope I was some help.

I like your recording idea. One customer that had problems with her instrument cluster that we could not duplicate had her camera running when the cluster acted up,we could no longer deny the problem existed.

The recording situation goes the other way,another customer was claiming noise from the cluster area,we could not duplicate on test drives so we had him show us. He removed the pickup for a hearing aid that he kept in his shirt pocket and placed it inside the cutout for the speedo,now we knew how he could hear the noise.

It’s fact that younger folks can hear a greater range of sounds than older folks can. There are even “dog whistle” recorded sounds that play outside of convenience shops in Britain to keep teenagers from hanging around out front. If this is a very high pitched sound and the mechanics were older than you they literally may not be able to hear it.

Yes, they did. Look up the TSB.

Sounds like the expansion valve. I believe there is a TSB on this. I don’t think it
leads to any kind of functional problem, just the unpleasant noise.

Sometimes it is very hard to diagnois a noise over the net. Even a mechanic standing next to the car could not give a answer. Giving directions to find the source of the noise also has value. Would you have prefered someone makeup a answer?

I will sign the payroll deduction that is being processed because I did not give a answer to this one. We do this for free so be happy if we just are able to give hints to get to the source of the problem and explain a possibility why the people that have been looking could not hear the noise.