High Pitch whistle

My 2004 Chevy Colorado Crew Cab (Z71) has a periodic high pitch whistle comming out of the Heating/Air Conditioning system. With the heat and air off the noise goes away. Any other Colorado owners experiencing this noise?

Dealer says vehicle is so new that no other reports have come in on this problem. Labeled it as normal vehicle noise. (NOT)

Same problem with mine, but it happens every 25 to 40 seconds. Took to dealer, friday, they say it is the shielding on the muffler. They had a call into tech support and said there is a "IP" report on this problem? Waiting on parts to come to dealer right now. Will let you know results when parts put on.

Mine does this as well. I believe it is the expansion valve on the Air conditioner. My buddy had this noise on a different vehicle and the dealer replaced the evaporator. I plan on waiting a while before going to the dealer, but it looks like I am not the only one with this issue. My air conditioner puts out plenty of cold air, but for how long?

Mine does this as well. It has done it from day one, about every 40 seconds with the AC on. I asked the service manager about the noise and he replied that the truck is so new they are not aware of any problems.

Let me know when someone gets this taken care of...mine does the same thing. :)

Took mine back to dealer, they thought maybe the expansion valve was the problem, changed it but still doing the same thing as before. Dealer told me they will have to wait for bulletin to come out. Anybody got any suggestions on how to get GM to move on this?

Took mine back to dealer, they thought maybe the expansion valve was the problem, changed it but still doing the same thing as before. Dealer told me they will have to wait for bulletin to come out. Anybody got any suggestions on how to get GM to move on this?

I think the only thing you can do is call GM Customer Service. Let them know to log the issue and that's it, unless your local dealership can handle it. Let me know what else you find.

Tx.
- Speedi

Took mine back to dealer, they thought maybe the expansion valve was the problem, changed it but still doing the same thing as before. Dealer told me they will have to wait for bulletin to come out. Anybody got any suggestions on how to get GM to move on this?

I finally got an answer from the dealer on the high pitched noise. There is a TSB 04-01-38-012A, that will solve the problem. Got my truck back today and have not had any noise. Hope this will help! Mine was still under warranty. Looks like they changed out the evaporator core. I will let you know if I have any problems.