Just something I've noticed as the weather has got damp and cooler.
The Mondeo's demister is absolutey superb if I use the air-con, the car being driveable even on a cold start within about 10-15 seconds. Trouble is, when I then turn off the air-con, the car slowly mists up again (over the space of 5 minutes or so), regardless of blower setting, temperature or air direction. The only way to clear it seems to be to turn the air-con on again (when it clears almost instantly)
This is not the first A/C equipped car I've had to suffer from this - just wondered if anyone had any idea why some A/C equipped cars seem to need the A/C on to stay demisted?
This morning (8°C) was particularly bad.
Cheers
DP
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Same with my car. I put it down to less ventilation in the cabin compared to older cars. Pollen filters etc restrict the flow.
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A/C dehumidifies the air as well as removes heat from it, so when a/c is turned off, the air rehumidifies, heats up, and condenses against the cold glass.
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Yes I've noticed the same thing on the loan cars I've had when mine was in for servicing. Xileno's explanation sounds very plausible.
Surely the answer is to open the passenger's window a fraction until the heater is up to speed? That's always been my solution, and it seems to work.
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The conditioned air blown out by a/c system is 'dry', and has had a lot of moisture removed from it. If you run your car with the a/c on for most of the time, the air inside the car will by drier than a car without an a/c system. When you get in your car and start breathing warm moist air around, it very quickly settles on the window, which quickly mists over.
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let me be the last to let you down....
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All that happening is that when you turn off the a/c all the water that's collected on the evaporator (the cold 'radiator') is then picked up by the incoming airstream. So you're rapidly humidifying the incoming air.
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Our Renault Scenic is particularly bad for this. Sometimes it will take a good few minutes to clear. There have been cases where i've been driving merrily along, turned on the fan and the screen will instantly mist up creating zero vision, very dangerous.
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There have been cases where i've been driving merrily along, turned on the fan and the screen will instantly mist up creating zero vision, very dangerous.
In most cars the a/c goes off if you turn the fan off (so the evaporator shouldn't be wet).
Check the evaporator drain is clear. Changing the pollen filter often helps too.
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The science of it as follows, cold air cannot hold as much moisture as warm air hence when warm air is in the proximity of a cold surface the moisture in the air condenses on to the cold surfaces.
This is the cause of misting problems in cars though fortunately it is also the process that allows aircon systems to work in the way that they do.
If turning aircon off it is best to do so before turning the engine off so as to maintain airflow over the condensor for a short while after the compressor has switched off and, if driving at the time, have the blower fan on highish to keep up the airflow though the car.
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Useful information, thanks all!
Cheers
DP
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The best way to reduce the effects of lingering condensation is to keep the inside glass areas as clean as possible.
Otherwise deposits gradually settle on the glass areas, arriving via the ventilation system and condensation "sticks" to the surface rather than rapdily dispersing.
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What\'s for you won\'t pass you by
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I would think another factor is that the rapid clearing of mist using Aircon relates, as said above, to the dehumidifying effect. However the glass is still cold, it will take much longer to warm the glass so that it is above the dew point. Thus when you switch off too soon the mist reforms on the still cold glass.
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Thinking about it, my pollen filter could probably do with a change - it's been in there about a year now. Will do that and see if it helps at all.
I understand how the air-con helps demisting. I was just confused as to why it seemed to promote re-misting as well. It's all become clear now though. (groan!) ;-)
Cheers
DP
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>>it seemed to promote re-misting as well.>>
It's also one of the reasons why the recirculating feature cannot be used in demist mode below about four of five degrees Celsius - when you turn the direction knob to demist the windscreen recirculating is disabled.
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What\'s for you won\'t pass you by
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It's best to leave the aircon on all the time anyway or at least use regularly. In the winter it also helps to keep the carpets dry and fresh.
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The best way to reduce the effects of lingering condensation is to keep the inside glass areas as clean as possible.
Yes I think thats the key; a few weeks ago I got some "Screenies" interior glass wipes, and now I can see the condensation forms more readily on the areas that I didn't clean as thoroughly.
Rich.
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It is actually poor memory - the only regular commuting in a car I did (before getting a co car with Aircon) was in the early 80s in a Sierra. Cold mornings were hell, waiting for the engine to warm up before it would de-mist, wiping the screen with cloths and watching it mist up again...... Who would do without aircon now!
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"It's best to leave the aircon on all the time anyway or at least use regularly. In the winter it also helps to keep the carpets dry and fresh."
And also I was told, it keeps the A/C seals lubricated.
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If anybody has some advice oh how to work out the a/c de-misting process of a honda civic i'd be very grateful.
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If anybody has some advice oh how to work out the a/c de-misting process of a honda civic i'd be very grateful.
Press the a/c button?
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Pretty much what I would have thought. Set output to screen and turn the a/c on.
On the Mondeo I don't get a choice. The a/c switches on automatically when the screen demisters are selected, and can't be turned off until the air is routed elsewhere. I can have demister and footwell together without air-con, which is how I tend to drive once the screen has demisted. Until it mists again as per my original post.
Cheers
DP
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Had a dreadful problem with this in my 1999 Accord.
Took the glove box off and changed the cabin airfilter (£8.00 from Unipart) and the difference is quite astonishing, no need for the A/C and the A/C itself blows a lot colder.
109K and never been changed by the looks of things....black and full of debris...yeuch!
Steve
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Surely all this is irrelvant on the mondeo? When the screen misted up I just used to put on the miraculous heated front window - how I miss that now.
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On the Mondeo I don't get a choice. The a/c switches on automatically when the screen demisters are selected, and can't be turned off until the air is routed elsewhere. >>
On mine I can direct air at the screen as well as, or instead of, the feet, face vents etc or select demist where the fans run faster and all is directed to the screen automatically, I hardly ever use the latter because the former does the job along with, if required, the heated screen.
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