Fogging windows

I have a 2002 Windstar Sport, 3.8L dual heat and A/C. On a recent trip through the Rogers Pass in a heavy rain/snow mix coming down, the only way we could keep the inside of the thing from fogging up was to crank the heat to hi and open both front windows an inch or so. Once the rain slowed down it cleared up with the windows shut. My question is, where and how can I check the drain on the evaporator case. I remember this was a problem on some of the cars I worked on in years gone by. I can't do it anymore so if anyone has some info I can get a buddy of mine to have a look.

ch

Reply to
golden oldie
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I think the fogging problem is more a result of saturated outside air being heated and drawn into a very hot interior. Moisture condenses on the relatively cold glass. Did you try running the AC or the defrost setting?

Reply to
John S.

Make sure you have the HV system on outside air, not recirculation.

Reply to
Don Stauffer

I respectfully disagree. In my experience the defrosters in most modern cars can keep up with high humidity air drawn in from outside, with or without the A/C running. However the OP describes one of the worst case scenarios, rain/snow mix which causes the maximum heat drain on the windshield. What's more relevant is whether you can tell if the behavior recently got worse compared to the same conditions historically.

Yes "ch", checking for a plugged evaporator drain is a good idea. Also look for plugged heater/defroster ducts in general, weak or broken flapper valves and linkages, and possible leaks allowing more rain water than normal to get into the air ducts and the heater core.

Yes John S, running the A/C WILL clear the windshield better, whether the system is set on outside air or recirculate, because the A/C condenses out humidity when running.

--Dave

Reply to
Dave Allured

A simple defroster can only do so much to compensate for the temperature differential which causes moisture trapped in the air to condense on the colder glass. Reducing the moisture content of the air or Signficantly dropping the inside temperature are the only two ways I know of to control moisture condensation on relatively cold glass.

The rain/snow/sleet are not causing the heat loss - the temperature is. The very moist outside air is making it's way into the car and is not being dried and exhausted properly. Combine that with a car full of breathing sweating humans and you've got a lot of humidity to deal with.

Given that it is snowing and sleeting my choice would be clearing snow buildup on air intakes.

Reply to
John S.

Wet carpets are one of the worst offenders for inside fogging and frosting, be sure they are dry and/or use those collector mats so you can dump then out when snow covered boots come inside.

Having the defrost on fresh air is also needed. Recirc and wet carpets, well you will need a squeegee or scraper on the inside of the glass for that.

Does your AC work? 'Most' modern vehicles automatically turn on the AC pump with the defrost setting to use it to dry the air out as it comes into the vehicle. If your AC has quit or doesn't function well, you can have more defog issues than normal.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 'New' frame in the works for '08. Some Canadian Bush Trip and Build Photos:
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Reply to
Mike Romain

"fogging windows"

I've heard a lot of people say that right before they hit Ctrl-Alt-Del.

Reply to
Matt

Thanks for your suggestions. ch

Reply to
golden oldie

I believe a rain-sleet mixture is a cause -- The melting ice needs heat for the process and drops the temperature significantly -- Wet carpet inside and wet clothes on the humans will add a significant amount of water vapor in the air.

One way to prevent fogging is to apply something to the glass that partially insulates it, like anti-fogging stuf used for eyeglasses or spitting in a dive mask -- Rain-X makes an interior glass coating that might work here.

Pete

Reply to
ratatouillerat

Therefore I throw structural compromise into the hat here - either the car was previously abused or hit, or the seals between members of glass and the openings were shot.

Reply to
ChrisCoaster

Maybe it was because "the car did not come with a defroster"?

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Reply to
jim

_______________________

That's IT - Jim!!! That's gotta be. Cause maybe if it did come with defroster, I should have left the car running with the defroster setting on overnight!

You're BRILLIANT - why didn't I think of that???

-CC

Reply to
ChrisCoaster

But, you did think of that and it was pretty dumb.

What you described is moisture accumulating inside the vehicle. A working defroster would prevent that from happening.

-jim

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Reply to
jim

There was a lot of moisture (not frost) on the inside of my 1983 Dodge van windshield and the drivers side window and front passenger side window this morning.I wiped it off with a towel.I didn't know Rain-X makes something for use on the inside of glass, I will try it out. cuhulin

Reply to
cuhulin

___________________ For cuhu: I tried that inside glass treatment a long time ago and it is a WASTE OF MONEY. It must be applied on a dry sunny day with humidity approaching 10% or less on a perfectly clean inside windshield or else it won't do a damn thing. Weather conditions like that are probably best found between Nevada and New Mexico.

As for Jim - he's more out of touch than Sarah Palin on the issue of the presence of a defrost mode or not. Even if that 71 Chevelle of mine DID come with a defroster the windows would have fogged up over night anyway, indicating some kind of leak between the inside and outside in that car. And even if I did run such defroster while driving the evening before and then parked the car for the night and drove it the next morning the fact that I ran the defroster the night before would not have prevented the build up of frost on the inside surfaces.

Yes, a defroster would have expedited the clearing of the windows of inside ice the next morning, but the point is - and I'm wasting my breath on Jim with this: THERE MIGHT HAVE BEEN A BREACH OF THE OUTSIDE/INSIDE BARRIER of that Chevelle, either around the windows or through the firewall or elsewhere that MIGHT have cause such buildup of ice inside its windows.

-CC

Reply to
ChrisCoaster

You do know that NO vehicle is actually sealed right? On your Chevelle that grill in front of the windshield feeds both of the floor vents and the heater with fresh air. Then if you opened the door you would notice the two flap vents in them and if you were to crawl into the trunk you would have found a set of vents that allowed air transfer through the cabin. The problem you had was due to a simple thing. Temperature differential and YOU. While your driving in a cold vehicle you turn on the heat. That causes the air inside to expand some. This air inside would also be laden with moisture from your breathing. Now you park the car and as it starts to cool it draws in more air through the venting system. The glass would have the fastest heat loss as well, that will draw the warmer moisture laden air to it through convection currents. The moisture hits the cold glass and freezes.

This is the reason that most vehicles built from 94-95 on have been set up to run the A/C during the defrost cycles. It drops the humidity levels in the vehicle and prevent the condensation on the glass. Presto no ice or fogging of the glass.

Reply to
Steve W.

__________________________ Then explain why the two 1981 Buick Centurys I drove during HS and college, my '96 Ford Contour, my '03 Impala, and my '05 Malibu never had ice on the insides of their glass when I went down in the morning to drive them to work, etc? A little fog build up - yes, but not solid coats of ice. __________________________

___________________________ Actually, I was under the impression that the only difference between a typical car's AC and Defrost functions was a matter of which way that air was routed - either through the dash vents(toward the occupants) for AC, or up through the vents on top of the dash(toward the windshield) for defrost/defog. Otherwise, I always believed that AC & defrost used the same compressor to condition the air, and that it was up to the driver to select the right mode & temperature via the knobs on the center stack - unless that car was equipped with Auto- Climate option.

-CC

Reply to
ChrisCoaster

A Chevelle did come with heater and defroster when it was new and if it was working like new it would keep the interior of the car dry enough so that it wouldn't fog up on the inside of the glass. I know for a fact there are plenty of cars from that era that made it thru Wisconsin winters without ever forming ice on the inside of the windows. The only ones that ever did that were the ones where the defroster wasn't functioning.

The moisture comes from the occupants of the car. If the heater and defroster are working it will drive the moisture out of the car. Did you think a car was so air tight that the occupants suffocate if they drive for more than an hour? A 71 Chevelle with properly working heat, defrost and ventilation will not form ice on the inside of the glass.

That is what you imagine to be the case.

-jim

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Reply to
jim

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As it turned out, the cabin air filter was very dirty which cut down on the air flow. I wasn't aware it had a cabin air filter. So, problem solved.

Chris

Reply to
golden oldie

The 81's had a flow though vent system that also had flap valves to prevent entry of exterior air unless you selected it on the controls. The 96 and up used the A/C core to pull the moisture out of the air. They also had much better body seals and controls as well.

Kind of. The way the current defrost system operates by running all the air through the A/C prior to passing it through the heater core. The defrost setting on most of the newer vehicles is also controlled through the electronics much more, between the BCM measuring interior humidity and temp and cycling the A/C and blend doors to control the interior temp. Even without the full auto controls the rest of the system is still there.

Reply to
Steve W.

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