My '05 does it. It sounds like a cop giving a quick blip to his siren, but obviously not as loud.

It happens randomly and not very often.

 

Exactly!! Hahaha....It's freaked out quite a few of my passengers over time.

I'm really glad you guys knew what I was talking about, I was sure it was going to be some obscure problem. With this many people reporting it, I'm surprised it isn't mentioned in detail anywhere on the site (or maybe it is and I haven't seen a post about it yet).

 

Just logged on to search for this issue, as my '04 AP2 does the exact same thing. I also was looking for cops in the rearview mirror - until I took it in, and they told me it was just a "noisy expansion valve".

 

My '04 makes noise from under the dash as well. I wouldn't call it a siren like sound. I think the noisy expansion valve is very likely. It does sound like a hissing.

 

It's not like a cop siren when they are chasing you down the freeway - more like when they "blip" the siren once - like a "whoop." I had someone look at it a couple of years ago - they put oil in the compressor, and the noise stopped for a while, but now is back. The system operates fine, so I'm just going to turn up th radio...

 

Mine made that noise and then my compressor went out. =(

 

Prior to hearing the expansion valve theory, I was thinking the noise was from a compressor bearing. I don't really have much of a clue and should look into it sometime.