My 97 960 has a big problem with moisture in the heater air. The inside was wet a month or more ago due to clooged sunroof drains, but we fixed that, dried it out well and haven't had it it wet since. Today, with the cooler weather we turned on the heater (not the defroster) and the windows immediately filled with heavy dew/moisture. I turned on the defroster and while it helped, it didn't solve it. Something is definitely wrong. So now home in the garage, there's no sign of moisture on the floor or mats, the moisture wipes clean with no signs of antifreeze and the antifreeze level shows no sign of leakage. The car has had a slight musty odor sonce we've owned it, but there's no sign of accumulated moisture that could be creating the foggy windows.

Where's the water hiding - or how is it the heater core cold be leaking without losing antifreeze or any signs in the car......??

I need some ideas.. please....and thanks!!

 

Was there a sweet smell coming out of the vents?
The heater core might be leaking.

 

No - but there is a strong musty/moldy smell when I run the heater.

I've checked the carpets and up under the passenger side for any signs of heater core leakage and don't see any. The antifreeze level is also unchanged. I also swiped the moisture off the windshield and it's more like water.

Another problem (and maybe the real problem) I noticed yesterday is the fan doesn't seem to be moving any air. It makes lots of noise - especially up under the passenger sie of the dash, but very little air is movning, regardless of whether it's directed to the defroster, dash vents or the floor (the direction controls did seem to work - but the air flow was way less than it shouild have been).

Any other ideas?

 

I wonder if the A.C drain is clogged and the case has water sitting in it.

 

Volvo's are designed to use the AC system to help keep the moisture down (all cars really). Does your AC work? If so, next time you turn on your defroster, flip the AC on and you'll see the glass clear up in seconds.

There is a chance that your fan motor is bad, maybe your fan blade has come loose (or broke loose) from the shank. Put your control **** to front vents, make sure your vents are open, turn the fan on high, if the wind will not blow out a match or blow paper to the back seat, you likely have a problem with your fan.

 

You can buy at various hardware stores a chemical dryer package that people use to dehumify basements, boats in storage, and other enclosed spaces. It comes in various sizes, too. And various brands. In a container that collects the moisture out of the air.

As your first post indicates a source of unwanted moisture, its quite possible that excess is still in the carpets, headliner, seats, etc.

Try this stuff. Ask at the hardware store. Open the package, leave it in the interior with the windows closed and sunroof closed. See if it starts to dehumidify the interior.
Cheap enough to try. Every winter we store wife's convertible with one Starbrite marine dehumidifier pack inside the interior and one inside the trunk Never ever had a moisture problem despite unheated garage storage.