Defogging in humid weather

Can someone please post the best method of defogging ones' winshield in
humid (hot) weather? I put my defogger on highest possible fan...and
the fog from the inside of the window goes away completely. However,
the winshield is still fogged up from the outside and refuses to go
away without the use of my wipers. Even then it does not go away
completeley (still a thin layer of fog)...and then returns fully in a
few seconds unless I keep my wipers on (even though its not raining).
I never had this problem before with my other cars. It only seems to
be happening on my new 2005 Honda Acoord. I spoke to a friend who also
purchased the same car...and he complaind of the same problem.
Neither blowing cold or hot air with or w/o the A/C seemed to get rid
of the outside fog. Any suggestions? Anybody else with the same
problem?

 

Yes, but it only happened to me once. I turned on my wipers to get rid of
it. Not sure how to prevent this from happening, except to possibly turning
the a/c a little warmer? It only happened once on my '05 Accord so I never
tested this method. Since it is happening on the outside I can only assume
it is the colder air from the a/c that is chilling the windshield, creating
this effect. Could this be the reason? I'm not sure but can't imagine what
else it could be.

-Dave

 

All the Hondas I have owned do this. The outer side of the windshield
gets cold enough to drop below the dew point of the ambient air, and
water condenses at the lower edge outside. Lack of heat coming off the
engine to the same area also allows snow and ice to build up there in
the winter. My old Pinto never had either problem. bob

 

Is this a design flaw by Honda? I see it as a safety issue...and if it
is a flaw they should issue a recall, shouldn't they?

 

Why is it a safety issue?

If moisture is on your windshield, use the wipers to wipe it off.

Or do you expect life to be perfect in all ways?

 

It's not a design flaw. Honda engineers have no control over the elements.
The problem is related to conflicting temperatures(interior vs. exterior)
and humidity. My son was just complaining about this exact same issue
yesterday after having driven his 1990 Nissan 300ZX in extremely humid
conditions. I've experienced this same problem with most all of my cars at
one time or another. I've just always relied on the windshield wipers--and
it will eventually clear up and stay clear during your drive. It doesn't
usually plague you for very long after you've ran the wipers for a while.

Ron M.

 

I have to agree..Just bought a CRV with 300 miles on it. Night time 68f 90%
humidity, no problem with clearing inside but outside had to use wipers and
it still left a film which built up right away with moisture. Cleaned window
on outside and inside with good glass cleaner to no help. Tried heat and
cold and all in between. The wipers need to run almost constantly, hell I
thought there was a leak in engine compartment...
Never had this problem with other vehicles on same night- Jeep Cherokee and
Taurus.....
Sounds like a safety issue to me....Something is not right.....

Thanks
Tom

 

Its not a safety issue at all. when you use your AC on cool to clear
the glass, you're clearing the inside, by removing the internal
humidity. however, the glass is cold enough to drop below the external
dew point. Solution - heat the windscreen up - that is what the
defrost setting on your car heater is for!. Warm the glass, its not a
proble. My experiance is that american vehicles (such as the taurus
and jeep0 tend to have thinner and/or less insulating glass, so the
gradient between in and out isn't so bad.

I have, however, had this problem on EVERY SINGLE CAR i've ever owned,
one time or another - and most of them don't and never have had, AC.
in those cases, you run the engine fora bit, get the inside warm, then
stick the wipers on intimittant, or use the manual single-sweep when
needed..

What is all this obsessing with 'this sounds like a safety issue' -
even *IF* it was, there would be no recall, since a solution (THE
WIPERS) are already included into the design of the car.

 

I agree with your comments on heat.
My point is I tried with the heat with and without recirc. and the problem
was still there...
I never noticed this before with other vehicles....

Tom

 

The issue with the "safety" is that it seems others, not just myself,
experience much worse windshield fog on Honda vehicles than other
models/makes. I drove a Camry, Maxima, and Caravan Minivans...and
don't recall a prob with the windshield fogging in any of them. While
I don't disagree with your assursion that it is cause by outside
elements, it still seems odd that Honda vehicles seem to be reacting
worse than others. The wipers don't help too much especially when
driving on 2-way roads, at night. The oncoming headlight glare
illuminates the fog and makes it hard to see even with the wipers on.
Hence, the saftey issue. It is possible that the Honda glass is
thicker (it does seem to be very thick..never compared though) and
therefore the problem is somehow exaserbated. I tried warming up the
windshield (set my inside temp to 77-78) but it actually worstened the
problem.

 

As i said, i've had it happen in every vehicle i've driven (within
reason). ESpecially when i was in the UK, as its humid, often cold,
and AC has only recently become standard.

It's hapened on golfs, volvos, austin/MGs, friends fiat panda was very
bad at doing it (but it had a weak heater), although the worst of the
lot was a 98 ford Fiesta zetec.

That being said, it does happen here in georgia too - i've had it
happen with my 88 civic, my 87 caravan, and a 96 T+Ci've been
passengers in friends vehicles when its happened to them - 88
silverado, 2001 venture, and an 05 camry. Its just how it goes.
trigger the wipers when its a problem - its just like light
rain/drizzle, (which is effectively what is is) and deal with it.

 

Happened all the time in my '93 Civic EX. Frequency likely depends
on what the dew point is typically like when you're driving, so it'd
be sensitive to location. I was mostly around Boston and Cincinnati
(and sometimes en route from one to the other, obviously), both of
which tend to be humid.

I admit that the first time it happened it took me a couple of
minutes to realize that the condensation was on the outside of the
window. It was the first day I had the car and I thought at first
that maybe I had a bad radiator and coolant vapor was leaking into
the cabin - a problem I'd had with an ancient Buick I used to drive
(somewhat affectionately known as the "Chernomobile", in honor of its
senendipitous fog-machine effects).

That should fix the problem. Reducing the fan speed once the inside
of the windshield is clear may also help. Turning the defogger on
full blast directs lots of cold air at the inside of the windshield,
which tends to cool the outside of the windshield, which causes
condensation. Simple, really.

Turning the air temp up will reduce the cooling effect, and unless
you're driving through a tropical monsoon shouldn't bother you.
Using a slower fan speed will reduce the forced convective cooling of
the inside of the windshield and allow the outside to retain more
heat.

 

I've had my Accord for under 2 weeks now . I'm sure it'll happen again
in the future - I'm in Maryland and we get all types of weather & temps
around here and there is no lacking of humidity. Live here and don't like
the weather? That's ok - just wait a day and it'll change.

That makes sense. I'll try that next time.

 

It may simply be that (some) Hondas leak less hot air from the engine
compartment out onto the base of the windshield, so it's easier to
chill the exterior of a Honda windshield.

Are you sure? Heating the windshield should not increase condensa-
tion. I can think of two explanations: it didn't actually aggravate
the condition (you imagined it, or it only worsened during the time
it took for the windshield's outside temperature to rise), or your
car has an actual defect and your problem *isn't* simple atmospheric-
moisture condensation. A leaking heater core, perhaps.

I can imagine that you might be driving under conditions where it's
not raining, the dew point is at or above 78 degrees[1], and there's
no other source of heat for the windshield exterior (it's not sunny,
for example), and so you might still get some condensation even with
the temperature set that high. (And may I say I'm glad I'm not
living under those conditions. Yuck.) But raising the temperature
from the minimum setting couldn't cause *more* condensation of
atmospheric moisture.


1. Actually, I bet the exterior of the windshield has to be somewhat
below the dew point for condensation to occur, if the vehicle is in
motion; otherwise air movement will allow the air flowing over the
windshield to be somewhat supersaturated with moisture. So the dew
point would probably have to be somewhat over the cabin temperature.
I don't know enough about water-vapor physics to guess by how much,
though.