The past few weeks, I have been hearing a water sloshing sound from inside the car. It sounds almost like there is a large-ish tub below the passenger seat filled halfway with water, which then sloshes as I drive the car. The sloshing is most audible when I accelerate and decelerate, and a bit less so when turning or going on slopes.

At first I wondered if it was gasoline moving inside the partially full tank, but that makes little sense. First, I've never heard it before, second, my gas tank is in the trunk and not below the passenger seat, third, the sloshing continues with a full tank.

There are no water bottles or similar containers in the car that would account for the noise.

I am now suspecting that the water is accumulating in the AC ducts:

  • It has been raining a lot lately and my AC has a mildew smell reminiscent of still water.
  • Earlier, when I had hot AC run for a while the sloshing lessened (water dried?). Unfortunately since then it rained even more and now the AC trick doesn't seem to work.
  • I noticed some dampness on the carpeting right in front of where the AC outlet for feet is, below the seat.
  • I've occasionally heard what sounds like splashing below the seat, which is consistent with a container that opens into the cabin.

Unfortunately, when I tried looking into the AC outlet and feeling with my fingers, I couldn't confirm nor deny this suspicion.

So there are three related questions here.

  1. How do I confirm it's really water in the AC?
  2. How do I get it out?
  3. Is this supposed to happen, or is something wrong with my car that led to this? The only thing that comes to mind is that weatherstrips at the bottom of my side windows have come off recently, but I couldn't say for sure if the sloshing is coming from the bottom of the car or from inside the door. The door doesn't seem to leak any water.
  • What is the year/make/model of the car? – Pᴀᴜʟsᴛᴇʀ2 Jan 5 at 18:35
  • If the door drain holes are blocked, then they will hold water and quite a bit... have a look along the inside edge and you should see them if they are there, a small wire or plastic cable tie is usually sufficient to push the crud out... – Solar Mike Jan 5 at 19:50

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