Front Windshield Fogs up fast?

[viper69]

My Volvo 850GLT, I love it! I have a Nissan Maxima, and under the exact same weather conditions I do not see any fogging of the front windshield ( I tested this last night, temps were about 44F) in the Maxima. In the Volvo it gets foggy within 10 minutes last night, even along the lower sides of the front driver and passenger windows. It was too foggy inside to drive safely. I was not even talking that much in the car during this time.

This is what I know about my Volvo

1. The radiator coolant has a TINY, and I mean, TINY leak somewhere. The liquid level goes below the line in the overflow tank after about 3-5 months depending upon frequency of driving and ambient air temperature (faster during the summer even w/less driving, summer temps ~75F). Leakage is so small, I can't find it on the ground.

2. The A/C works fine.

3. The RECIRCULATE button while operational doesn't actually close the fresh air vents. The vents are always open. When the Recirc is turned on, I can hear a little gear sound behind the glove compartment box, but whatever is moving doesn't close the vents.

4. The water drainage conduits up by the windshield wiper arms, under the hood, are clean of debris, water flows out nicely.

5. There is no dampness on the front or rear floor of the interior cabin.

6. Turning on the Defogger w/all the front facing vents closed, takes the windshield about 20-30 minutes to clear up to be safe to drive at night. The A/C wasn't much shorter in time, just colder.

What do people suggest could be wrong?

[cn90]

Search forum for "ebay heater core"...

[misha]

2. The A/C works fine.
3. The RECIRCULATE button while operational doesn't actually close the fresh air vents. The vents are always open. When the Recirc is turned on, I can hear a little gear sound behind the glove compartment box, but whatever is moving doesn't flows out nicely.

6. The A/C wasn't much shorter in time, just colder.

2.Does it?
3.It seems that air recirculation is stuck closed.How do you know that it's always open?
6.It doesn't work or you have HUGE amount of moisture from heater core leak...or it's just No.3.

[ThommyKent]

Heater core leak, doesn`t take much

[abscate]

There is so much padding and foam on these cars that the leaking coolant from the heater core collects under the rear seats and does not soak the carpets. You have to lift the carpet and padding to find it.

[viper69]

Search forum for "ebay heater core"...

Thanks!

[viper69]

2. The A/C works fine.
3. The RECIRCULATE button while operational doesn't actually close the fresh air vents. The vents are always open. When the Recirc is turned on, I can hear a little gear sound behind the glove compartment box, but whatever is moving doesn't flows out nicely.

6. The A/C wasn't much shorter in time, just colder.

2.Does it?
3.It seems that air recirculation is stuck closed.How do you know that it's always open?
6.It doesn't work or you have HUGE amount of moisture from heater core leak...or it's just No.3.

2. Yes it does.
3. I always feel air coming in through vents whether the amber light is on or off. Also, when the amber light is on, indicating the vents to the cabin are closed (according to the manual) I can still smell exhaust from nearby trucks/cars at times when in other vehicles I've owned I could not.
6. I see.

[viper69]

There is so much padding and foam on these cars that the leaking coolant from the heater core collects under the rear seats and does not soak the carpets. You have to lift the carpet and padding to find it.

Thanks I didn't realize that.

I loosely know what the heater core is. Why does a broken heater core cause condensation on the glass? I assume it's a temperature difference of some air (coming from the core?) vs the temperature outside and thus the glass, warmer air against cold glass.

Second, does the condensation left on the glass end leave a thin residue on the glass that appears as if the glass is foggy even if it isn't? Sort of like an ultra-think layer of grease (or film) (minus the light scattering distortion grease would cause) ?

[RussB]

When a heater core leaks,the fan will blow humid air onto the windshield, causing it to condensate. Doesn't matter if the climate control is set to recirc or not

[viper69]

Thanks Russ!