whistle in the rear area 02' tahoe

[wgburton]

My 2002 Tahoe whistles in the rear cabin area when the ac is on. It is not constant, it seems to do it the most when I'm stopping or starting to move and sometimes softer while I'm driving but, not as frequent. I have rear ac and the auto control front ac.c. I've played with different settings and nothingseems to make it go away.
It's driving me crazy. Sometimes it sounds like a cop is behind me. It freaks me out! The first time I noticed it, I pulled over because I thought it was a cop. Not cool!

Any ideas? I don't want to spend a fortune as I just replaced the cats and knock sensors along with all the intake stuff that was involved with that.

 

[Rivieraracing]

Sounds like you need to have someone sit back there and listen for a better idea of where the noise is coming from!

 

[wgburton]

Sorry, I should have said that I have done that. It is coming from the rear ac area. I am thinking it is the thermal expansion valve. I just want to get some other ideas before I go tearing into this thing. I hate throwing money at a problem blind.

 

[wgburton]

I've checked everything in the back. Removed the panel, the actuators/ blend doors are working properly and making no irregular noise. The AC blows cold as it should but the noise is ridiculous and annoying. The refrigerant lines are hot even when the system is blowing cold. I believe it has a bad thermal expansion valve...
So, I am going to go through the pain of replacing it. I have researched it online and it looks like fun. ANyone else deal with this? Any suggestions?

 

[Mr.Jack]

Have you ever serviced the AC system?
I had a whistling sound/ high frequency sound whenever I turned on the AC.
My shop said it could be that the system was low on AC gas.
Had it serviced yesterday, and the sound is gone.
Just a thought.

 

[wgburton]

When I bought it a couple months ago, I used one of those AC chargers that you buy at the store with the gauge. It wasn't cooling well, and was reading low from that gauge. I don't know how reliable that thing is. I'm going to have a friend of mine hook it up at his shop and check the levels. If tweaking is necessary and fixes it, I'm going to leave well enough alone and stop messing with it. I really hope that is all it is.
If it continues, I'm going to get him to recover all the r134 from the system so I can replace the TXV on my own, then just get him to vacum it and recharge. Like I've said, I cant dump much more money into this one.

 

[Mr.Jack]

Let us know how it goes. If something of the same happens to us.

 

[ccapehartusarmyINF.(ret)]

turn the radio up

 

[99RGV_Denali]

What happened with this afterall? same thing on my 99 Denali, it is the rear ac assembly making the sound, I shut the a/c button off and it goes away so it has to do with refrigerant. What was it after all? It cools nicely on highway just not at a dead stop.