I've noticed a sort of swoosh noise coming from under the dash with the AC on during cool weather. It occurs like every 2 or 3 minutes. I'm not sure if I'm hearing the AC compressor cycle off or if it a valve under the dash (maybe controlling hot water flow). The noise only happens with the AC on.
Has anyone else experiensed this? It's hard to describe the noise acurately - and I haven't spent a lot of time investigating this yet (it just got "cool/cold" in FL). Never heard any noise like this during the hot summer months.

 

I think what you are hearing is only because of damper (door) position in the heat-exchanger. The source of noise can be air in the coolant, which would make gurgling sound. With the engine COLD open the radiator cap and peer down the hole. Use distilled water to fill up and if you have to add more than cup, then you should add conc coolant or instead you can use the premix. I would suggest that you use toyota coolant.

Salim

 

If what you are hearing is a hiss from the expansion valve, then it is normal to a degree.