we have an '07 S type and am hearing a 'gurgling' noise coming from under the passenger side dash. was wondering what this might be?

 

MDJag, normally when you get a sound like this, it is following long term use of the A/C system. What you are hearing is water inside the catch tray not being able to escape out the drain tube and the air blowing through the system is causing the water to be moved. You may note that it will seem to take a long time for the water to finish draining out from under the car after you have stopped. This is another sign that your drain is plugged.

What needs to be done is to clear the drain line. You can do this by either getting under the car and pushing something backwards through the drain line to push the blockage back into the catch tray or use a wand of some sort, going in through an access point inside the car and using a small amount of compressed air, push the blockage all the way out.

Once you get the blockage removed and the system drained, you can open the windows and turn on your A/C system. Then at the opening of the ventilation system (base of the windshield), you can spray in some Lysol. This will go through the ventilation system of the car, killing off any sort of mold/mildew that may have formed (what normally causes the blockage). Just don't be sitting in the car as the fumes can get somewhat strong. Let the ventilation system run for an additional 10 minutes or so after you are spraying and then leave the windows open for another hour or so.

Someone else may have another idea. So, don't take this as gospel.