windshield defogger -- cool air in warm weather w/o A/C?
 

When the windshield defogger is operating in my 2003 Accord (on
a cool temperature setting), and the A/C is apparently off (the
A/C indicator lamp is unlit), I note that really cool air comes
out of the upper dash vents even in mid-80s weather. The air is
so cool, especially when the car's interior is not hot, that I
find myself not even needing to activate the A/C!

What is the source of this cool air? Is the A/C system actually
operating in tandem with the windshield defogger on the cool setting?

Paul

Re: windshield defogger -- cool air in warm weather w/o A/C?
 

Yes it is. The purpose being to dehumidify the air.
Adjust the temperature setting to suit.



mike hunt

Paul Stuart wrote:
>
>Is the A/C system actually
> operating in tandem with the windshield defogger on the cool setting?
>
> Paul

Re: windshield defogger -- cool air in warm weather w/o A/C?
 

Yes it is. The purpose being to dehumidify the air.
Adjust the temperature setting to suit.



mike hunt

Paul Stuart wrote:
>
>Is the A/C system actually
> operating in tandem with the windshield defogger on the cool setting?
>
> Paul

Re: windshield defogger -- cool air in warm weather w/o A/C?
 

It actually is the reverse........use the recirc air button once the air is
cold inside the cabin......make the ac work less as it is recirculating
cooler air. Don't use the recirc button until the air is cool.....and open
the window for a few moments to have hot air escape faster


"bearman" <noyb@home.com> wrote in message
news:Yr2cnWhSMeDilt-iU-KYuQ@comcast.com...
>
> I thought we were supposed to run the a/c in recirc (with a window open to
> get rid of the warm air) when first starting it to cool down quicker then
> switch to Fresh. Seems like running in recirc all the time would cause
the
> interior air to get pretty stale and maybe even dangerous.
>
>
> "Paul Stuart" <pstuart03@hotmail.com> wrote in message
> news:b46b8f39.0308190228.2578785b@posting.google.c om...
> > BigJohnson@mailcity.com wrote in message
> news:<3F412874.34017441@mailcity.com>...
> > > Yes it is. The purpose being to dehumidify the air.
> > > Adjust the temperature setting to suit.
> >
> > Hello, Mike!
> >
> > Thanks for your information. Because I thought the A/C system was
> > inactive before receiving your response, I was hoping that I had found
> > a way to actually conserve the use of the system and compressor
> > during warm days.
> >
> > When I need a quick cool off on hot days, I let the A/C run for a few
> > minutes on Fresh Air mode to cool off the interior, then I press the
> > Recirc button and adjust the temperature setting to a warmer one.
> > With the Recirc and warmer setting, the system and compressor would not
> > need to work as hard to continue cooling, which I think is better for
> > the system in the long run.
> >
> > I also get slightly better fuel economy when I do this. I note that
> > I travel about 360 miles on 12 gallons of 87 octane, which is about
> > 30 mpg, with very little of this highway driving. I think I might
> > get better mileage during the winter, but I'm not so sure, because
> > these New Jersey gas stations use oxygenated fuels starting in November.
> >
> > Paul
>
>

Re: windshield defogger -- cool air in warm weather w/o A/C?
 

It actually is the reverse........use the recirc air button once the air is
cold inside the cabin......make the ac work less as it is recirculating
cooler air. Don't use the recirc button until the air is cool.....and open
the window for a few moments to have hot air escape faster


"bearman" <noyb@home.com> wrote in message
news:Yr2cnWhSMeDilt-iU-KYuQ@comcast.com...
>
> I thought we were supposed to run the a/c in recirc (with a window open to
> get rid of the warm air) when first starting it to cool down quicker then
> switch to Fresh. Seems like running in recirc all the time would cause
the
> interior air to get pretty stale and maybe even dangerous.
>
>
> "Paul Stuart" <pstuart03@hotmail.com> wrote in message
> news:b46b8f39.0308190228.2578785b@posting.google.c om...
> > BigJohnson@mailcity.com wrote in message
> news:<3F412874.34017441@mailcity.com>...
> > > Yes it is. The purpose being to dehumidify the air.
> > > Adjust the temperature setting to suit.
> >
> > Hello, Mike!
> >
> > Thanks for your information. Because I thought the A/C system was
> > inactive before receiving your response, I was hoping that I had found
> > a way to actually conserve the use of the system and compressor
> > during warm days.
> >
> > When I need a quick cool off on hot days, I let the A/C run for a few
> > minutes on Fresh Air mode to cool off the interior, then I press the
> > Recirc button and adjust the temperature setting to a warmer one.
> > With the Recirc and warmer setting, the system and compressor would not
> > need to work as hard to continue cooling, which I think is better for
> > the system in the long run.
> >
> > I also get slightly better fuel economy when I do this. I note that
> > I travel about 360 miles on 12 gallons of 87 octane, which is about
> > 30 mpg, with very little of this highway driving. I think I might
> > get better mileage during the winter, but I'm not so sure, because
> > these New Jersey gas stations use oxygenated fuels starting in November.
> >
> > Paul
>
>

Re: windshield defogger -- cool air in warm weather w/o A/C?
 

Actually you have it backward. One should run on fresh (outside)
air to pull in outside air and push out the hot air within, when
using Air conditioner. Once the vehicle begins to cool, go to
recirc to re-cool the dehumidified air inside the vehicle. There
is always an infusion of some outside air in any event. In the
defrost mode the air source is from outside. If you vehicle has a
manual recirc/fresh (outside) air controller, the recirc should
only be used for AC, not heating, or your will build up
humidity. Read your owners manual for complete instruction of
the operating of the HVAC system, WBMA


mike hunt



bearman wrote:
>
> I thought we were supposed to run the a/c in recirc (with a window open to
> get rid of the warm air) when first starting it to cool down quicker then
> switch to Fresh. Seems like running in recirc all the time would cause the
> interior air to get pretty stale and maybe even dangerous.
>
> "Paul Stuart" <pstuart03@hotmail.com> wrote in message
> news:b46b8f39.0308190228.2578785b@posting.google.c om...
> > BigJohnson@mailcity.com wrote in message
> news:<3F412874.34017441@mailcity.com>...
> > > Yes it is. The purpose being to dehumidify the air.
> > > Adjust the temperature setting to suit.
> >
> > Hello, Mike!
> >
> > Thanks for your information. Because I thought the A/C system was
> > inactive before receiving your response, I was hoping that I had found
> > a way to actually conserve the use of the system and compressor
> > during warm days.
> >
> > When I need a quick cool off on hot days, I let the A/C run for a few
> > minutes on Fresh Air mode to cool off the interior, then I press the
> > Recirc button and adjust the temperature setting to a warmer one.
> > With the Recirc and warmer setting, the system and compressor would not
> > need to work as hard to continue cooling, which I think is better for
> > the system in the long run.
> >
> > I also get slightly better fuel economy when I do this. I note that
> > I travel about 360 miles on 12 gallons of 87 octane, which is about
> > 30 mpg, with very little of this highway driving. I think I might
> > get better mileage during the winter, but I'm not so sure, because
> > these New Jersey gas stations use oxygenated fuels starting in November.
> >
> > Paul

Re: windshield defogger -- cool air in warm weather w/o A/C?
 

Actually you have it backward. One should run on fresh (outside)
air to pull in outside air and push out the hot air within, when
using Air conditioner. Once the vehicle begins to cool, go to
recirc to re-cool the dehumidified air inside the vehicle. There
is always an infusion of some outside air in any event. In the
defrost mode the air source is from outside. If you vehicle has a
manual recirc/fresh (outside) air controller, the recirc should
only be used for AC, not heating, or your will build up
humidity. Read your owners manual for complete instruction of
the operating of the HVAC system, WBMA


mike hunt



bearman wrote:
>
> I thought we were supposed to run the a/c in recirc (with a window open to
> get rid of the warm air) when first starting it to cool down quicker then
> switch to Fresh. Seems like running in recirc all the time would cause the
> interior air to get pretty stale and maybe even dangerous.
>
> "Paul Stuart" <pstuart03@hotmail.com> wrote in message
> news:b46b8f39.0308190228.2578785b@posting.google.c om...
> > BigJohnson@mailcity.com wrote in message
> news:<3F412874.34017441@mailcity.com>...
> > > Yes it is. The purpose being to dehumidify the air.
> > > Adjust the temperature setting to suit.
> >
> > Hello, Mike!
> >
> > Thanks for your information. Because I thought the A/C system was
> > inactive before receiving your response, I was hoping that I had found
> > a way to actually conserve the use of the system and compressor
> > during warm days.
> >
> > When I need a quick cool off on hot days, I let the A/C run for a few
> > minutes on Fresh Air mode to cool off the interior, then I press the
> > Recirc button and adjust the temperature setting to a warmer one.
> > With the Recirc and warmer setting, the system and compressor would not
> > need to work as hard to continue cooling, which I think is better for
> > the system in the long run.
> >
> > I also get slightly better fuel economy when I do this. I note that
> > I travel about 360 miles on 12 gallons of 87 octane, which is about
> > 30 mpg, with very little of this highway driving. I think I might
> > get better mileage during the winter, but I'm not so sure, because
> > these New Jersey gas stations use oxygenated fuels starting in November.
> >
> > Paul

Re: windshield defogger -- cool air in warm weather w/o A/C?
 

<StonyRhoads@lycos.com> wrote in message news:3F4263FA.B88A4F91@lycos.com...
> Actually you have it backward. One should run on fresh (outside)
> air to pull in outside air and push out the hot air within, when
> using Air conditioner. Once the vehicle begins to cool, go to
> recirc to re-cool the dehumidified air inside the vehicle. There
> is always an infusion of some outside air in any event. In the
> defrost mode the air source is from outside. If you vehicle has a
> manual recirc/fresh (outside) air controller, the recirc should
> only be used for AC, not heating, or your will build up
> humidity. Read your owners manual for complete instruction of
> the operating of the HVAC system, WBMA


Good advice.
Mine says to open a window for sec to dump the hot air, and run the A/C in
recirc.
Even says to run in recirc for fast heating, but switch to fresh if things
begin to fog up.

1991 Honda Accord Owners Manual




>
>
> mike hunt
>
>
>
> bearman wrote:
> >
> > I thought we were supposed to run the a/c in recirc (with a window open
to
> > get rid of the warm air) when first starting it to cool down quicker
then
> > switch to Fresh. Seems like running in recirc all the time would cause
the
> > interior air to get pretty stale and maybe even dangerous.
> >
> > "Paul Stuart" <pstuart03@hotmail.com> wrote in message
> > news:b46b8f39.0308190228.2578785b@posting.google.c om...
> > > BigJohnson@mailcity.com wrote in message
> > news:<3F412874.34017441@mailcity.com>...
> > > > Yes it is. The purpose being to dehumidify the air.
> > > > Adjust the temperature setting to suit.
> > >
> > > Hello, Mike!
> > >
> > > Thanks for your information. Because I thought the A/C system was
> > > inactive before receiving your response, I was hoping that I had found
> > > a way to actually conserve the use of the system and compressor
> > > during warm days.
> > >
> > > When I need a quick cool off on hot days, I let the A/C run for a few
> > > minutes on Fresh Air mode to cool off the interior, then I press the
> > > Recirc button and adjust the temperature setting to a warmer one.
> > > With the Recirc and warmer setting, the system and compressor would
not
> > > need to work as hard to continue cooling, which I think is better for
> > > the system in the long run.
> > >
> > > I also get slightly better fuel economy when I do this. I note that
> > > I travel about 360 miles on 12 gallons of 87 octane, which is about
> > > 30 mpg, with very little of this highway driving. I think I might
> > > get better mileage during the winter, but I'm not so sure, because
> > > these New Jersey gas stations use oxygenated fuels starting in
November.
> > >
> > > Paul

Re: windshield defogger -- cool air in warm weather w/o A/C?
 

<StonyRhoads@lycos.com> wrote in message news:3F4263FA.B88A4F91@lycos.com...
> Actually you have it backward. One should run on fresh (outside)
> air to pull in outside air and push out the hot air within, when
> using Air conditioner. Once the vehicle begins to cool, go to
> recirc to re-cool the dehumidified air inside the vehicle. There
> is always an infusion of some outside air in any event. In the
> defrost mode the air source is from outside. If you vehicle has a
> manual recirc/fresh (outside) air controller, the recirc should
> only be used for AC, not heating, or your will build up
> humidity. Read your owners manual for complete instruction of
> the operating of the HVAC system, WBMA


Good advice.
Mine says to open a window for sec to dump the hot air, and run the A/C in
recirc.
Even says to run in recirc for fast heating, but switch to fresh if things
begin to fog up.

1991 Honda Accord Owners Manual




>
>
> mike hunt
>
>
>
> bearman wrote:
> >
> > I thought we were supposed to run the a/c in recirc (with a window open
to
> > get rid of the warm air) when first starting it to cool down quicker
then
> > switch to Fresh. Seems like running in recirc all the time would cause
the
> > interior air to get pretty stale and maybe even dangerous.
> >
> > "Paul Stuart" <pstuart03@hotmail.com> wrote in message
> > news:b46b8f39.0308190228.2578785b@posting.google.c om...
> > > BigJohnson@mailcity.com wrote in message
> > news:<3F412874.34017441@mailcity.com>...
> > > > Yes it is. The purpose being to dehumidify the air.
> > > > Adjust the temperature setting to suit.
> > >
> > > Hello, Mike!
> > >
> > > Thanks for your information. Because I thought the A/C system was
> > > inactive before receiving your response, I was hoping that I had found
> > > a way to actually conserve the use of the system and compressor
> > > during warm days.
> > >
> > > When I need a quick cool off on hot days, I let the A/C run for a few
> > > minutes on Fresh Air mode to cool off the interior, then I press the
> > > Recirc button and adjust the temperature setting to a warmer one.
> > > With the Recirc and warmer setting, the system and compressor would
not
> > > need to work as hard to continue cooling, which I think is better for
> > > the system in the long run.
> > >
> > > I also get slightly better fuel economy when I do this. I note that
> > > I travel about 360 miles on 12 gallons of 87 octane, which is about
> > > 30 mpg, with very little of this highway driving. I think I might
> > > get better mileage during the winter, but I'm not so sure, because
> > > these New Jersey gas stations use oxygenated fuels starting in
November.
> > >
> > > Paul

Re: windshield defogger -- cool air in warm weather w/o A/C?
 

"Larry" <zieglerl@pacbell.net> wrote in message news:<ass0b.2415$Gi6.179310767@newssvr13.news.prod igy.com>...
> It actually is the reverse........use the recirc air button once the air is
> cold inside the cabin......make the ac work less as it is recirculating
> cooler air. Don't use the recirc button until the air is cool.....and open
> the window for a few moments to have hot air escape faster

Whether you're recirculating air or not, your air conditioning system
is still working just as hard. Your air conditioner is either on or
off, there's no (or very little) difference in the amount of work
required. When you have your internal temperature warm or cold,
recirculating or not, you're AC system is working just as hard. The
only way to reduce the amount of fuel consumption is to not use AC.

If you know how air conditioners work, the COMPRESSOR compresses a gas
(R134 or equivalent) within the cooling system. It requires energy to
compress the gas, which is supplied by your engine (via a
belt/pulley). When this gas is allowed to expand, it gets very cold.
This entire cycle is contained within it's own system so that gas
isn't lost.

Re: windshield defogger -- cool air in warm weather w/o A/C?
 

"Larry" <zieglerl@pacbell.net> wrote in message news:<ass0b.2415$Gi6.179310767@newssvr13.news.prod igy.com>...
> It actually is the reverse........use the recirc air button once the air is
> cold inside the cabin......make the ac work less as it is recirculating
> cooler air. Don't use the recirc button until the air is cool.....and open
> the window for a few moments to have hot air escape faster

Whether you're recirculating air or not, your air conditioning system
is still working just as hard. Your air conditioner is either on or
off, there's no (or very little) difference in the amount of work
required. When you have your internal temperature warm or cold,
recirculating or not, you're AC system is working just as hard. The
only way to reduce the amount of fuel consumption is to not use AC.

If you know how air conditioners work, the COMPRESSOR compresses a gas
(R134 or equivalent) within the cooling system. It requires energy to
compress the gas, which is supplied by your engine (via a
belt/pulley). When this gas is allowed to expand, it gets very cold.
This entire cycle is contained within it's own system so that gas
isn't lost.

Re: windshield defogger -- cool air in warm weather w/o A/C?
 

In article <Yr2cnWhSMeDilt-iU-KYuQ@comcast.com>,
"bearman" <noyb@home.com> wrote:

> I thought we were supposed to run the a/c in recirc (with a window open to
> get rid of the warm air) when first starting it to cool down quicker then
> switch to Fresh.

Nope. Open the windows and set to fresh air. Once the superhot air has
left the inside of the car, and the car is at outside temperature, close
the windows and set to recirculate.

You need to exhaust the superhot interior air before the A/C can really
do any good.

Re: windshield defogger -- cool air in warm weather w/o A/C?
 

In article <Yr2cnWhSMeDilt-iU-KYuQ@comcast.com>,
"bearman" <noyb@home.com> wrote:

> I thought we were supposed to run the a/c in recirc (with a window open to
> get rid of the warm air) when first starting it to cool down quicker then
> switch to Fresh.

Nope. Open the windows and set to fresh air. Once the superhot air has
left the inside of the car, and the car is at outside temperature, close
the windows and set to recirculate.

You need to exhaust the superhot interior air before the A/C can really
do any good.

Re: windshield defogger -- cool air in warm weather w/o A/C?
 

Elmo P. Shagnasty wrote:
> In article <4031f12e.0308191312.26ed29e6@posting.google.com >,
> audi4sale2k@yahoo.com (Mike S) wrote:
>
>>Whether you're recirculating air or not, your air conditioning system
>>is still working just as hard. Your air conditioner is either on or
>>off, there's no (or very little) difference in the amount of work
>>required.
>
> Well, there's the difference between the temperature of the expanded
> refrigerant as it comes into the compressor, and the temperature of the
> compressed refrigerant as it leaves the compressor. That difference is
> how hard the compressor works.
>
> The smaller the difference, the less hard the compressor has to work to
> re-compress the refrigerant.
>
> If you're simply cooling already cool air, on recirculate, then the
> difference is minimized and the compressor doesn't work as hard. But if
> you're always cooling 90 degree air from the outside, the difference is
> greater and the compressor works harder.
>
> Then there's the "how humid is the outside air" argument. If you're
> bringing in a lot of moisture, the evaporator can easily ice up as it
> removes that moisture. That will definitely happen much more easily
> with fresh air than recirculated air.
>
> Face it: in your house, you never bring in fresh air via the air
> conditioning and heating system, do you? You're always recirculating
> the air and re-conditioning it. The only fresh air that comes in, does
> so from leaks (windows, etc.) and when you open the door.
>
> So if you're not worried about it in your house, why worry about it in
> your car?

The interior of the car is what - 2-3% of the interior volue of your
house? Plus you have many materials in the car not usually seen in a
house. I don't think this is a very good comparison. There's also a huge
difference in how they're expected to operate, e.g., a house may take
hours to cool, whereas if the car isn't cold in 5 minutes, the %^&$$%^&
a/c is broken!

FWIW, everything I've read over the years has recommended opening a
window and running on RECIRC when starting up a car with a heated
interior, then closing the window and switching to FRESH. With the
windows (& moonroof, if present) closed, there isn't much fresh air
coming in, just equal to what the cabin vents permit to escape
(otherwise the interior would get pressurized and it would be like scuba
diving).

Finally, as the a/c compressor cycles on & off, it's consuming
significant power only when it's running. The fan runs constantly and
consumes *much* less power than the compressor.

Re: windshield defogger -- cool air in warm weather w/o A/C?
 

Elmo P. Shagnasty wrote:
> In article <4031f12e.0308191312.26ed29e6@posting.google.com >,
> audi4sale2k@yahoo.com (Mike S) wrote:
>
>>Whether you're recirculating air or not, your air conditioning system
>>is still working just as hard. Your air conditioner is either on or
>>off, there's no (or very little) difference in the amount of work
>>required.
>
> Well, there's the difference between the temperature of the expanded
> refrigerant as it comes into the compressor, and the temperature of the
> compressed refrigerant as it leaves the compressor. That difference is
> how hard the compressor works.
>
> The smaller the difference, the less hard the compressor has to work to
> re-compress the refrigerant.
>
> If you're simply cooling already cool air, on recirculate, then the
> difference is minimized and the compressor doesn't work as hard. But if
> you're always cooling 90 degree air from the outside, the difference is
> greater and the compressor works harder.
>
> Then there's the "how humid is the outside air" argument. If you're
> bringing in a lot of moisture, the evaporator can easily ice up as it
> removes that moisture. That will definitely happen much more easily
> with fresh air than recirculated air.
>
> Face it: in your house, you never bring in fresh air via the air
> conditioning and heating system, do you? You're always recirculating
> the air and re-conditioning it. The only fresh air that comes in, does
> so from leaks (windows, etc.) and when you open the door.
>
> So if you're not worried about it in your house, why worry about it in
> your car?

The interior of the car is what - 2-3% of the interior volue of your
house? Plus you have many materials in the car not usually seen in a
house. I don't think this is a very good comparison. There's also a huge
difference in how they're expected to operate, e.g., a house may take
hours to cool, whereas if the car isn't cold in 5 minutes, the %^&$$%^&
a/c is broken!

FWIW, everything I've read over the years has recommended opening a
window and running on RECIRC when starting up a car with a heated
interior, then closing the window and switching to FRESH. With the
windows (& moonroof, if present) closed, there isn't much fresh air
coming in, just equal to what the cabin vents permit to escape
(otherwise the interior would get pressurized and it would be like scuba
diving).

Finally, as the a/c compressor cycles on & off, it's consuming
significant power only when it's running. The fan runs constantly and
consumes *much* less power than the compressor.