Does your Gen 3.5 do this? AC thing. . .

[73sport]

Windows Fog after AC use:
I'd guess the average humidity around here is in the 50% range. I never see the AC make puddles and I know the drain is not plugged. But with the windows up, AC on (which blows 40F on medium fan speed on a 100F day with 50/50 cabin/outside air), when I switch AC Off, the cabin instantly becomes humid. Depending on the outside temp, it MAY fog the front and/or side windows.

Because of this, I end up washing the front window monthly. When defrosting the window on a cold morning, the AC helps, but as soon as I switch it off, it instantly fogs with humidty.

IS this normal? Does your car do this? I partially pulled the cover near the evap core where the drain pipe attaches and its clear of obstruction. Heating and cooling works fine other than when I switch the AC = OFF!

Strange or Normal?

*EDIT: the car is not full of water anywhere, i.e. trunk, doors, carpet ect. . .

Thanks,
73

[Nervous]

There does the fog appear - on outside or inside surface? AC should DE-humidify the cabin, that is how it actually works. But since it is hot and humid outside you may have a condensation on outside surfaces of glass (hot air contacting cold glass).

[73sport]

Originally Posted by Nervous

Where does the fog appear - on outside or inside surface? AC should DE-humidify the cabin, that is how it actually works. But since it is hot and humid outside you may have a condensation on outside surfaces of glass (hot air contacting cold glass).

I know and agree that's what it's supposed to do! Its the inside and its done it since I've owned it.

Does yours make a humid swelter AFTER switching the AC button off?

[Nervous]

Oh, I misread the first post. Yes, if I turn AC off then it starts to blow humid air also.

[BMR]

Mine does this too, although here in CO the humidity's usually so low it's not a prob. I suspect what happens is that when the system's running, the evaporator has lot of condensate on it. When it's shut off, the warm air flowing thru the evap starts picking up the residual moisture and makes the air more humid than it was to start with. Then that humid air hits the chilly window and voila, fogged up window.

[73sport]

Originally Posted by BMR

Mine does this too, although here in CO the humidity's usually so low it's not a prob. I suspect what happens is that when the system's running, the evaporator has lot of condensate on it. When it's shut off, the warm air flowing thru the evap starts picking up the residual moisture and makes the air more humid than it was to start with. Then that humid air hits the chilly window and voila, fogged up window.

Excellent explanation and exactly how I'd been thinking after seeing the drain was not plugged.

Add this to that explantion: the guy that owned it last for like a year was smoker. Before that, unknown. You know how that stuff clings? Maybe theres like a build up on the evap that holds moisture thus the reason it drips so little to the outside and DUMPS the humid cloud back into the cabin when the cooling is shut down? Hint only seen it puddle on real humid days.

The cars that do this Humid dump thing, would you rate the cabin ducts as clean or perhaps having years of accumulation? Years ago I pulled the dash and cleaned most of the air delivery ducts but nothing down at the blower mtr or evap core.

[Stillrunning]

Originally Posted by 73sport

AC on (which blows 40F on medium fan speed on a 100F day with 50/50 cabin/outside air), when I switch AC Off, the cabin instantly becomes humid.

A/C off and fan still on with 50% outside air?

[projektvertx]

As a matter a fact, I just experienced this minutes ago myself. It's pouring rain and condensation was forming on the windshield. A/C, condensation gone. As soon as I turned the A/C off but left the air on med., I saw stripes of condensation where the air vents are... So yes, I've just assumed it's normal.

[73sport]

Quote:
Originally Posted by 73sport
AC on (which blows 40F on medium fan speed on a 100F day with 50/50 cabin/outside air), when I switch AC Off, the cabin instantly becomes humid.

Originally Posted by Stillrunning

A/C off and fan still on with 50% outside air?

Me no understand Although I pretty much always leave the fresh/recirculate mixer in the center giving 50% fresh and 50% recirculate if that clears things up.

When its above 90 I may slide it to recirculate 100%

[93celicaconv]

73sport: You did say you are discharging 40F air temp to the windshield. This is pretty cold. Remember that the glass will retain this cold (or slowly get warmer after the AC compressor is shut off), so any air that you blow by it with the fan still running (AC off) or just cabin air, where that air's due point is above 40F, it will start condensing out on the coolest object below the air's dew point.

I would turn your temperature control up a bit to get your air wrmer when you primarily use it to defrost the windshield. This way, your 40F air coming from your evaporator will pass through your heater core and, while it still warms up, it will keep the dew point temp. down to no more than 40F when it discharges. That way you will keep your windshield a bit warmer and lessen the chance that it will fog up after your turn your AC off.

[73sport]

Originally Posted by 93celicaconv

73sport: You did say you are discharging 40F air temp to the windshield. This is pretty cold. Remember that the glass will retain this cold (or slowly get warmer after the AC compressor is shut off), so any air that you blow by it with the fan still running (AC off) or just cabin air, where that air's due point is above 40F, it will start condensing out on the coolest object below the air's dew point.

I would turn your temperature control up a bit to get your air wrmer when you primarily use it to defrost the windshield. This way, your 40F air coming from your evaporator will pass through your heater core and, while it still warms up, it will keep the dew point temp. down to no more than 40F when it discharges. That way you will keep your windshield a bit warmer and lessen the chance that it will fog up after your turn your AC off.

Thanks, yes for defrost the heat is on too & the AC for pulling the moisture (rare, but sometimes). Its summer now so the big question is do other cars drowned you in a humid bath after chopping compressor power/cooling. Does your Celica do this? What temp does it blow?

Mind you, only use the AC a dozen times a year here and half the time I do it with the windows down BUT w/windows up, cabin goes instantly stuffy right after AC cut blower still on.

Tks

[eyeball96]

I run the AC with outside air only, and I have never experienced what you describe.

Todays high was 101 with 43% humidity.

[93celicaconv]

Originally Posted by 73sport

Thanks, yes for defrost the heat is on too & the AC for pulling the moisture (rare, but sometimes). Its summer now so the big question is do other cars drowned you in a humid bath after chopping compressor power/cooling. Does your Celica do this? What temp does it blow?

Mind you, only use the AC a dozen times a year here and half the time I do it with the windows down BUT w/windows up, cabin goes instantly stuffy right after AC cut blower still on.

Tks

I guess I never checked my outlet temps when I have the defrost on. I know I don't run 40F air up against the windshield though. Probably more like 55-60F air during a summer defrost need. I know that if I run max cold against the windshield, it will fog up when the A/C is turned off also, so I never set it that cold when defogging. As soon as the windshield is clear, though, I don't keep the defroster on, I got to dash vents and turn the temp down a bit. Always works well for me.

And yes, I typically always pull outside air in, never recirculate cabin air (unless it is bitterly cold or terribly hot initially, then I will recirculate until the temps are more bareable, then will go with outside air only. I heard from a few techs that running recirculated air all the time will cause mold in the evaporator coil, because it never drops out enough moisture to wash the coil clean (outside air will do this, supposedly).

[eyeball96]

Originally Posted by 93celicaconv

I guess I never checked my outlet temps when I have the defrost on. I know I don't run 40F air up against the windshield though. Probably more like 55-60F air during a summer defrost need. I know that if I run max cold against the windshield, it will fog up when the A/C is turned off also, so I never set it that cold when defogging. As soon as the windshield is clear, though, I don't keep the defroster on, I got to dash vents and turn the temp down a bit. Always works well for me.

And yes, I typically always pull outside air in, never recirculate cabin air (unless it is bitterly cold or terribly hot initially, then I will recirculate until the temps are more bareable, then will go with outside air only. I heard from a few techs that running recirculated air all the time will cause mold in the evaporator coil, because it never drops out enough moisture to wash the coil clean (outside air will do this, supposedly).

I had that problem

The previous owner of the Coupe always kept it on recirculate

[fenixus]

Originally Posted by 73sport

Windows Fog after AC use:
I'd guess the average humidity around here is in the 50% range. I never see the AC make puddles and I know the drain is not plugged. But with the windows up, AC on (which blows 40F on medium fan speed on a 100F day with 50/50 cabin/outside air), when I switch AC Off, the cabin instantly becomes humid. Depending on the outside temp, it MAY fog the front and/or side windows.

Because of this, I end up washing the front window monthly. When defrosting the window on a cold morning, the AC helps, but as soon as I switch it off, it instantly fogs with humidty.

IS this normal? Does your car do this? I partially pulled the cover near the evap core where the drain pipe attaches and its clear of obstruction. Heating and cooling works fine other than when I switch the AC = OFF!

Strange or Normal?

*EDIT: the car is not full of water anywhere, i.e. trunk, doors, carpet ect. . .

Thanks,
73

not sure we are talking about same thing, but here is what i observed on 3 different cars (which had a/c functional hehe):

a) when i use a/c to remove morning mist/fog after sunrise (because of sun heating up the nightly moist and temp change outside car vs inside car) by using defog mode which blows cold air directly onto windshield then once i turn it off the outside of windshield at bottom starts fogging (i have to use wipers intermittently to get rid off that).
i think that is because a/c in defog mode blows cool air on inside of windshield while the outside is heated up by sun (be careful, don't force to much temperature difference outside vs inside as it may crack the windshield eventually, seen it happen on 2 old fleet vans/trucks).

b) on a hot day and a/c blowing at low fan towards inside of car, eventually all glass (and everything else inside) gets colder on the inside of car than on outside, also since you are breathing the air in car with windows rolled up there is moist in it (more or less that's the CO2), so if temp outside is very hot (again temp difference in glass on outside and inside), but this time moist is on the inside of all glass, so once you turn off the a/c then the fogging may occur inside car on all windows.
also there is an effect like when something heats up rapidly (think of cold beer taken out of the fridge), so all the cold parts of car inside start heating up fast once the fan starts blowing hot & humid air from the outside then fogging occurs even more.

I noticed both scenarios to become more true in more humid climates, like florida. in jersey i see it mostly on a very hot & humid days.