My air conditioner makes a loud whistling noise that sounds like its coming from behind or under the dash on the passenger side. Its blowing fine, but is very annoying. Anyone ever had this problem?

 

My wife's car did that once - drove me nuts trying to figure out what it was. I searched for vacuum leaks under the dash, hunted around with a stethoscope trying to figure out exactly where it was coming from, you name it, I tried it.

Turned out to be a piece of a candy bar wrapper up in the blower motor housing.

Take a logical approach and rule out one thing at a time -
Does it make the sound no matter what it on (A/C, vent, heat, defrost)?
If it's just one, which one?
Does it make the sound when the climate control is off?
Does the sound change with different fan settings?

 

I initially though maybe something was inside the ducting. Its only on when the A/C is on full blast. I guess I'll try to tear her down today.

 

You might put an ear up to each vent and see if it's louder at one particular vent. That might give you a place to start. If it sounds the same in all the vents, maybe there's something in the fan housing in the blower motor.

 

Well for some reason I cant get it to make the noise again so hopefully it will stay gone, lol.

 

Maybe it fixed itself!

...too bad trannies never do that.