it's normal, all cars make that hissing noise. It's just the two pressure sides of the a/c system equaling out.
Thanks, I'll rep you for that. I was about to have to get in here and start dispelling some AC myths, all of which are pet peeves of mine.
Yes, the sound is refrigerant hissing into the evaporator. You likely have a clogged orifice tube exacerbating the situation- which is typical, and not to be concerned with until the system stops blowing cold air. If you really want to learn AC's, and the noise is really annoying to you, then read my thread, pull your system apart, replace the O-rings, orifice tube, vacuum, and recharge. It will end up costing you about $200 to DIY including special tools. Then you can impress all your friends by fixing AC systems in cars because it works the same way (although some parts have different names, yet do the same job) with the biggest difference being in how the systems are sealed.
