foggy windshield in rain - not an AC problem

petrhick · Post by **petrhick** » 04 Nov 2010, 17:25

I've looked all over but haven't found a post with a similar problem.
My windshield fogs up slowly in the rain (it takes a couple of minutes to fog up) no matter where I set the climate control, except on defrost, which works fine. Problem is that when it's cold outside and raining, I have to keep the defrost on most of the time (so my feet freeze) and I have to keep switching back and forth every couple of minutes between defrost and some other heat setting to warm up. I'm NOT losing coolant, I'm not smelling coolant. Not a problem when outside temp is above 60 or so.
I've tried all the different climate control settings available, I tried recirculating air and not, I tried different temp settings, nothing works for very long, except defrost which uses the AC and forces air in from the outside (will not recirculate air).
Other issue is that when I have fan on high and air coming in from the outside, there's a very loud howling noise coming from the left side behind the dash. It does not make the noise if I set the system to recirculate air.
Any ideas would be appreciated.
1998 V70 GLT

jbrown122 · Post by **jbrown122** » 04 Nov 2010, 17:54

Make sure the drains for the windshield aren't clogged up with leaves, dirt, etc

FCPEURO · Post by **FCPEURO** » 04 Nov 2010, 20:11

+1

If they are, and the water is not draining correctly, moister will get sucked into the air intake for the vents and fog the wind shield from the inside.

Post by **jblackburn** » 04 Nov 2010, 21:27

Do you lose antifreeze? You might have a leaky heater core (it goes on all of these cars around this age/150K miles), which can cause windows to fog up pretty quickly.

On fresh air mode, the inside shouldn't fog up - though I have seen it happen on like 50-60 degree days with the heater on a little bit; recirculate will do it rather quickly.

waynej · Post by **waynej** » 05 Nov 2010, 22:42

Mine was doing the same thing-turned out to be the recirc valve. I noticed there was no difference in fan noise between recirc and fresh. Moved switch back and forth with engine and fan off and could hear servo motor working properly. Pulled glove box and found little white plastic arm that goes between servo motor and valve was broken where it should attach to servo motor. Pulled it to full fresh position and wedged it in tight between two other things. No more fog!

V70Johnson · Post by **V70Johnson** » 06 Nov 2010, 05:04

Yep, I have the same issue with my '00 V70. Truly perplexing and I too have checked out all the possible causes & have yet to locate one.

Retired MVS Contributor · Post by **Retired MVS Contributor** » 06 Nov 2010, 06:11

There is a ventilation outlet at the left rear quarter panel under the corner of the bumper...There is usually a rubber flapper and if that becomes non-functional fogging will result...P2 models have two of them and they can be reached from inside under the rear floor...

petrhick · Post by **petrhick** » 06 Nov 2010, 06:25

Will check behind glovebox, but I can hear fan noise change when switching between recirculated and outside air.
Air intakes are clear, pollen filter is new.
I did find that if I keep the AC on and recirculate air it works much better, but it doesn't make much sense to me to have to run the AC in the winter....

Retired MVS Contributor · Post by **Retired MVS Contributor** » 07 Nov 2010, 12:10

petrhick wrote:Will check behind glovebox, but I can hear fan noise change when switching between recirculated and outside air.
Air intakes are clear, pollen filter is new.
I did find that if I keep the AC on and recirculate air it works much better, but it doesn't make much sense to me to have to run the AC in the winter....

It does make sense to run the air conditioner in cold weather, in fact automatic climate control systems are designed to do just that...The AC evaporator condenses the moisture out of the air keeping it from fogging the windows...The condensed moisture is drained to the outside...The heater core, which will be warm, keeps the condenser from icing...As recommended by the manufacturer, running the AC year 'round keeps the AC compressor seals, o-rings, etc from drying out, hardening, and leaking...It does not run constantly and the amount of gas used is negligible...

waynej · Post by **waynej** » 07 Nov 2010, 13:56

[quote="jerrymcc"]
It does make sense to run the air conditioner in cold weather, in fact automatic climate control systems are designed to do just that...The AC evaporator condenses the moisture out of the air keeping it from fogging the windows...The condensed moisture is drained to the outside...The heater core, which will be warm, keeps the condenser from icing...As recommended by the manufacturer, running the AC year 'round keeps the AC compressor seals, o-rings, etc from drying out, hardening, and leaking...It does not run constantly and the amount of gas used is negligible...[/quote]

jerrymcc,
I think you mean, to keep the evaporator from icing. The condenser is always hot when the compressor is running. You are definitely right about it being wise to run the AC in winter, if you don't you can get a leak. Three of my four Volvos have the manual climate control and I very seldom need to turn on the AC. If petrhick always has to run AC to defrost then something is wrong unless he lives in an extremely humid climate.

petrhick,
You need to check for plugged drains. Besides the 2 big drains you see at the firewall, you will see 2 more when you lift the big cover to get to the cabin air filter.