E46 interior humidity issue

OK, the fog in my E46 is approaching ridiculous at this point. This morning I had to scrape ice off the inside of the windshield.

For the last 3 weeks or so, I've had excessive moisture in the cabin, of unknown origin. When parked outside overnight, all 6 windows will fog up, sometimes very heavily. It does not seem related to rain or precipitation, there are no obvious leaks or damp spots inside, and I don't sweat that much. It doesn't smell of antifreeze.

If I drive to work (25 minutes +/-) with the defroster on full blast, including A/C, it will usually clear, but it comes back again overnight, or two. I recently bought a container of Damp-Rid to see if that works to get rid of the moisture for good, or if it comes back.

Any thoughts or similar experiences? Thanks.

Isn't that a sign of a leaking heatercore?

Do you normally drive with the HVAC in recirc mode? My brother did that with my Tercel years ago, and I would have massive frost inside. Took weeks to get rid of, since I was too cheap to warm it up and then let it idle with the heat on high and the windows cracked (to let the moisture escape. Also, check the AC drain, as the car may UtomTically use the AC without any outward indication when it is on defrost.

blown heater core or evaporator?

I'll check the A/C drain on the evaporator, that's a good idea. I have been assuming that if the heater core was the issue, I would smell coolant.

I normally do not drive in recirc mode and as far as I know am not now, though the climate control is a bit too automatic for my tastes.

My old E46 328i did the same thing, as is my current E46 M3 - the windows are iced up on the inside, and although the doors have been opened a time or two it hasn't been started in 2 months. No heater core leaks on either one.

Query - do you run with the AC on all the time in winter? I do that on all my cars - that's the only way I was able to control it on the 328i, and the various Honda products we had as well.

If you don't smell the sweet smell of antifreeze - check to see if the drains are blocked and pouring water into the carpet under the core or in from the wiper wells.

Also, the sunroof drains - they will soak the carpet and matt behind the front seats.

Once the carpet gets a couple gallons of wet - it takes forever to dry out after you fix the source. A powerful wet vac is helpful but still... a dry 100F week of sunshine with the windows down is best.

Put a plug in room dehumidifier inside the car and let it run overnight. That should warm things up and get all the water out of the car. Then you need to make sure that the A/C system is working okay and running while in the fresh air mode. Could it be possible that the system is discharged?

Giant Purple Snorklewacker wrote: If you don't smell the sweet smell of antifreeze - check to see if the drains are blocked and pouring water into the carpet under the core or in from the wiper wells. Also, the sunroof drains - they will soak the carpet and matt behind the front seats. Once the carpet gets a couple gallons of wet - it takes forever to dry out after you fix the source. A powerful wet vac is helpful but still... a dry 100F week of sunshine with the windows down is best.

I have not noticed any wet carpets, but I will check again. Definitely no antifreeze smell, though it smells like burning power steering fluid and oil (those are a different story).

Can you clue me in on where the AC and sunroof drains are located? Thanks.

jimbob - the AC is not discharged, and blows nice cold air. I do not run it full time, but it I do run it when running the defroster.

Generally the sunroof drains run down through the A-pillars, and the a/c drains out somewhere around the top of the transmission hump.

You can ream out the sunroof drains with a length of weed wacker string or something similar. The a/c drains are usually difficult to get to, but if the carpets are dry you're probably okay.

There's a fair bit of sound deadening material under the carpet, and it will absorb a lot of water. It's worth pulling up a bit of the carpet to make sure it's really dry under there.

The sunroof drains are often a problem, but not as often as the vapor barriers behind the door cards. If these have ever been disturbed (not at all unusual, given BMWs window regulator issues), they are very likely allowing water into the cabin.

Is the recirc door doing what its supposed to do? If its open, and the motor isn't moving it, thats bad.

Heater core will make this glass slimey. If you lick the windsheild, it will taste bad.

My Subaru Outback does this all the time.

It is not my DD, so I believe that it has to do with condensation from sitting around under the sun, changes in temperatures and the frameless windows.

Giant Purple Snorklewacker wrote: Also, the sunroof drains - they will soak the carpet and matt behind the front seats.

Looks like this may be the winner. Unfortunately it looks like the bottom of the seat may have some wetness in it too.

Anybody have protips for rodding these things out? I bought a spool of trimmer line, but I can't make it take the right-angle bend just inside the front drains... and I can't even find the rear drain inlets.

Do I need to take out the headliner? Please Bob no.

Are you sure they need to be rodded out? I found that the rubber drain had come undone from the sunroof on our touring. It was a 20min job to pull the A pillar cover, visor and reach to fix it. It's worth a look....

vapor barrier in doors leaking - glue can let go over time?
how about compressed air for the sunroof drains?

My major issue is that I'm pretty sure it's the rears that are clogged, and I can't even see the inlets. Plus, I don't have a compressor, even if I could find them. I guess I'll have to pull the b-pillar covers and see the status of the rubber hoses, and remove those if necessary to clean farther down. I was just hoping to avoid disassembling the interior.

I'm pretty sure it's the rears, not the fronts, because the water is in the rear footwells and under the rear seat.

I know the door barriers can be an issue too, but to my knowledge, the doors have never been apart. I also park under a sycamore tree so I am more likely to have clogged drains. Thanks, guys.