How can I fix/prevent damp car interior?

January 8, 2013 4:45 PM

It's a 1999 Honda Civic Hatchback. Apparently cars of this type and age have a tendency to develop a leak around the tail lights. This leak was fixed recently but the car either hasn't dried out from that yet or is damp *again.* The windows are perpetually fogged up and often need towelling and the seats (fabric) are suspiciously cool. How to dry it out and keep it that way? Thank you!
posted by srs airbag to grab bag (16 answers total)

Sounds like this might do the trick
posted by exogenous at 4:54 PM on January 8 [1 favorite]

Maybe something like this dehumidifier? You'll see others at that site, that was just the first one I came across.
posted by jvilter at 5:21 PM on January 8

I don't know anything about a honda civic, but I had a nasty surprise the last time I had a flat tire in my ancient (and now departed) toyota corolla wagon; I went to get it out and the depression under the cargo area where the spare was stored had a good two, three inches of water in it. Which explained to me why I'd never been able to get rid of the moisture inside my car either. So if that kind of set up is something you have - you might want to take a look there.

and if you want to try a dehumidifier, just buy some ice melt that's calcium chloride and put a few flat pans in your car over night. I've used it in small not-very-sealed spaces and it worked pretty well.
posted by lemniskate at 5:25 PM on January 8 [2 favorites]

You can get a product called DampRid at a hardware store (or on Amazon etc), which is meant to dehumidify closets or small rooms. It comes in a little tub that you leave open on the floor, and I think they also make sachets on a hook for hanging up. Some reviews mention fumes, so take it out of the car once it's done its job.
posted by bcwinters at 5:31 PM on January 8 [2 favorites]

Search around for "silica gel" and "dessicant." See if you can get them in bulk. Silica gel can be dried in an oven and re-used; I don't know if this is true of other chemical dessicants.
posted by eritain at 5:36 PM on January 8

Depending where you live, it's easy to bring a lot of water in on your shoes as snow. And then if you have a short commute, the car never gets warmed up enough to evaporate much of that water, and it just builds up. A good long drive (an hour or so) with the heater cranking and the fresh air / recirc. lever set to fresh air can help a lot.
posted by jon1270 at 5:44 PM on January 8

Run the air conditioner to dehumidify the air. You should see some water dripping under the car after it's been working for a while.
posted by ryanrs at 5:44 PM on January 8

What lemniskate said. I had a same-vintage Integra with the same kind of leak, and was really surprised when I found two inches of water in the spare tire compartment. Pull out all the carpet and everything from that area and shop-vac any standing water out of there!
posted by xil at 6:03 PM on January 8

Your car, if it has an air conditioner, already has a dehumidifier built right into it. Run it on Max AC with the fan turned up all the way, and then with the heat turned up somewhat. That will take the moisture out of the air pretty quickly, and out of the seats and most exposed surfaces in a few hours. There's no reason why you can't combine this with chemical dessicants too, but I suspect that the gasoline that it will take to run the car at idle for a few hours is less than the cost of most chemical dessicants.

I'd definitely check to make sure you don't have puddles of water somewhere inside the car, though ... the spare tire compartment would be the biggest one, but also check all the drain plugs in the doors to make sure they're not holding water.

N.B.: Some cars air conditioners don't function very well when the cars aren't moving, although this is more an issue on hot days. In the winter you shouldn't have too much of a problem, I'd imagine. I've heard of people using big fans to blow air across the condenser coils to test-run the AC while stationary, but not sure how effective that is.

If it doesn't seem to work and particularly if there isn't water dripping out after an hour or so despite cool air blowing from the vents (when the heat is turned off), then you should check the air conditioner condensate drain. That's another possible source of water in the car too.
posted by Kadin2048 at 6:08 PM on January 8

Yes, check the spare tire well. If you can't get rid of the water there (ie it comes back after driving in wet conditions), then it is still coming in somewhere else. Could be the little valves under the rear bumper.
posted by ssg at 6:09 PM on January 8

One small thing you can do: always select the control for "vent" (the arrow running through the car) instead of "recirculation" (the bent-backwards-on-itself arrow). ALWAYS. Even if you have the AC or the heat on, keep it on vent.

(I found out about this after I had constant trouble with the interior of the all windows on my car badly fogging up every single day.)
posted by easily confused at 6:13 PM on January 8

The spare tire compartment on our 95 Civic hatch was always full of water because of this issue. Our mechanic tried a few things to fix it, but ultimately the easiest thing for us to do was wet-vac out the back after heavy rain.
posted by Sidhedevil at 6:16 PM on January 8

The spare tire compartment was a problem but has been cleaned out. The car has no AC. Thanks for pointers to other possible issues in the car, and drying-out tips - will do.
posted by srs airbag at 7:16 PM on January 8

If you can't find or afford chemical dessicants, then plain old rice attracts water too.

If you had had an air conditioner, I would also have suggested checking your pollen filter. When they become blocked they allow water ingress.
posted by MuffinMan at 1:16 AM on January 9

You might want to check the seal around the back door. Improper alignment, debris, dry rot, etcetera.

We had the taillight problem in our Accord sedan, but the real culprit was the trunk seal.
posted by Mr. Yuck at 8:29 AM on January 9

possibly unrelated, but is there snow where you are? perhaps the moisture from the snow that you track into the car is trapped inside.

i was told to keep newspapers under the floormats, which will help to absorb some of the moisture. you would need to replace them regularly.
posted by bitteroldman at 9:10 AM on January 10