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Why do my windows constantly fog up on my 1998 Volvo S70 when they are up?

(1998 Volvo S70)
in Canfield, OH on December 13, 2012
Even when the defroster is on the windows constantly fog up until I drive with the windows downs. It has become dangerous now in the cold weather.
I've replace the pollen filter. The blower and temp work fine. Is it the recirculation switch or flap under the plastic cowl intake? I took it off the cowl ran the car with the blower & temp on and the flap on the recirculation never move when I engaged it. It moves freely like it is no attached to anything.
Thanks George.
Displaying 3 answers & 6 comments
Popular Answer
on December 17, 2012
You likely have a leaking heater core. Is there a sweet smell from the vents when running the fan? Is your coolant level slowly dropping?
on December 17, 2012
There is no smell of antifreeze in coming from he blower vents. The antifreeze level has not dropped. There is nothing in the passenger compartment or on the floor or under the engine compartment.
There is only this constant squeaking sound coming from the area of the air intake under the plastic cowl.
How do I check about a vacum leak on the heater control?
on December 17, 2012
There are no vacuum controls on the HVAC system, it's all electronic motors. Exactly where is the noise coming from?

The heater core is under the center of the dash. I would still want to look at it to see it's not leaking. It doesn't take much to fog up the windows. The heater core is just to the right of the accelerator pedal. Pull the carpet down and the plastic side panel off, and you'll see the heater core. If it's leaking, you'll see some signs.
on December 17, 2012
The sound comes from under the dash on the passenger side somewhere near the fire wall. It sounds like somethings or flap is trying to open and close.
on December 17, 2012
There is an air recirculation door that allows fresh air into the cabin, or recirculates inside air. Silly question, are you sure it's a S70 and not an S90?
of Greg's Orange Auto on December 13, 2012
poss vac leak at heater control valve or controller
on December 14, 2012
How do I fix this issue? Thanks George
on December 13, 2012
Is the air conditioning compressor working? That is what dehumidifies the air even when the temp is on warm (when defrost is selected).
on December 14, 2012
The air conditioning and the compressor all work fine. No leaks. The temp control works fine. The blower motor works fine. The is no loss or leak of anti freeze. The heater core does not leak. I have heard a sound of a sqeaking constantly whenever the car in on like a vacum constantly moving something.
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