2006 Tucson: question about defrost/defog

Hello

5 years ago I bought an Accent GSi. I got it in the middle of winter,
and I noticed that everytime I turned on the defog mode, the a/c light
would come on. I got the dealership to disconnect that since I was
under the impression the a/c compressor sucks a lot of gas.

I just picked up my Tuc a few days ago and noticed it does the exact
same thing. Does the a/c thing affect gas consumption when heat is
blowing out instead of cold air? Can I disconnect this without having
to go to the dealership? Should I not bother?

Thanks for your input

Alex

 

Leave it alone. The AC dries the air and is part of the defrost system.
Modern cars are mostly economical in the AC systems and do not
use up the fuel like a generation ago.

 

This same subject was discussed just a few days ago.

Untrue. The A/C dries the air, but that not only does no good when
you're trying to clear the OUTSIDE of the windshield, it reduces the
defroster's effectiveness. If you live up north, it sucks.

If you use the defroster to clear the inside of the windshield, then
switch to heat once it's clear, the moisture on the condenser coils gets
pumped back into the interior of the car and fogs up the windows again.
For that reason, I prefer to use heat to clear the windows in the winter.

Having the A/C compressor running costs me at least 3 mpg in my Elantra.
IMO, that's unacceptable for a "feature" that I don't even want.

Unfortunately, this is no longer something that can be easily
disconnected. I contacted Hyundai about it when I had a nasty experience
with it, but they had nothing to offer. In '04 and up, US market
vehicles, the only way to get around this is to splice a switch into the
A/C control line that comes out of the heater control module, so you can
manually turn the compressor off. It's an inexpensive modification, but
it requires removal of the dash facia and a bit of wiring. The switch I
used fits where the cigarette lighter was. Since the car has an
accessory socket, I didn't mind sacrificing the lighter to get better
defroster function.

 

Sure, it affects gas consumption some as it is drawing power from the
engine. However, most modern compressors are pretty efficient. I'd be
surprised if it made 1/2 MPG of difference. And the increased defogging
efficiency is worth it. Hitting something you can't see impacts your
gas mileage a lot more than running the compressor for a few minutes.
And once the windshield is clear, you often get enough defrost airflow
even on the normal heat setting to keep it clear.


Matt

 

This "feature" has been in place with most automobiles since the early
'90s. However, the majority of vehicles disable the AC compressor
below a certain temperature not only to protect the compressor due to
low ambient temps, but also not to degrade the defrosting abililty. In
my 1994 Dodge Grand Caravan ES it disables the compressor when the
outside ambient temp is below 30 degrees F. The AC light is on when
the outside temp is below 30 degrees, but the compressor is disengaged.
I haven't tested this on our new 2006 Elantra, but I would be very
suprised if this is not the case with Hyundai as well. Otherwise, all
of us who own Hyundai's will be replacing AC compressors at a rapid
rate!

Turning on the AC in the defrost mode helps the defogging ability of a
defroster tremendously by removing the interior humidity. Assuming the
disengagement of the AC compressor at low temps, this is actually very
good engineering.

 

*** Update ***

and I noticed that everytime I turned on the defog mode, the a/c light
would come on. I got the dealership to disconnect that since I was
under the impression the a/c compressor sucks a lot of gas.

same thing. Does the a/c thing affect gas consumption when heat is
blowing out instead of cold air? Can I disconnect this without having
to go to the dealership? Should I not bother?

Unlike my previous car, I found out this morning that I simply had to
press the a/c to disengage it! On the Accent, you could press all you
wanted on the a/c switch but it would always be on. Anyway, I'll be
testing it in the next few days and keep you all informed.

Again, thanks for the replies!

Alex

 

Elantra 02, and Santa Fe 03, they both work same way, push the buttom, A/C
goes OFF.

It's a nice feature , here in Florida, were the humidity is always high,
maybe not so much in the frigid norther tundra .....

 

odd I life up north.. and I have NO problem with that at all.. when in defog
mode. ya just turn the temp up .. problem solved...

Pete...

 

had an 04 Elantra GT, now have an 06 Santa Fe.. pushing the A/C button does
not turn it off any longer as it did in my Elantra... but still no big
deal.. still works the same. clears the windows.. thats what its for..;-)

Pete...

 

Something is seriously wrong then with your vehicle. I've never seen
the AC consume even 1 MPG on a modern car. Actually, on my minivans and
pickup, I can't even tell the difference between using AC and not. I
check every tank MPG all year around and the extra gas used by the AC in
the summer is lost in the noise of the MPG readings.

Matt

 

From my understanding, after the temperature drops below a certain
temperature (usually about 32 degrees) the A/C compressor does not
switch on in the defrost mode.

John

 

If only it were that simple. I got into a situation in freezing rain
where the defroster could not keep the windshield clear. Another 10 or
20 degrees in the temp of the air from the defroster would likely have
made all the difference in the world. Canadian market Hyundai vehicles
allow the A/C compressor to be switched off, which tells you something
about the effectiveness of this dubious "feature" in cold climates.

 

Sorry Matt, but I'm not buying that and I've never heard anyone else
make such a claim. An A/C compressor takes several horspower to run,
which does impact fuel mileage. There is still a debate about whether
rolling down the windows reduces fuel mileage more than using the A/C,
but there is no debate about the fact that either one reduces fuel mileage.

Perhaps you do a lot more city driving than I do, where the mileage drop
is less obvious, but a 3 mpg drop on the highway is normal.

 

That's what I thought too, but you can feel it kick in, both in the drag
that it causes and the difference in the air temp. If it does cut out
completely, it's apparently at a point that's too low, IMO.

 

That's true, but only IF you need it. It's not always necessary.

The devil is in the details. In the Elantra, it doesn't cut out at a
high enough temp to suit me. It definitely adversely affects the
defroster's ability to keep the outside of the windshield free of snow
and ice, especially when the temp is just below the freezing mark.

Additionally, I object to being FORCED to use the defroster this way. I
used to use the A/C combined with the heater or defroster in my ex-wifes
car WHEN I NEEDED IT, but you don't have the option to choose when to
use it in the Elantra. Well, at least you don't in a stock Elantra.
After the modification I made, I can control mine and use it only when
it's beneficial.

 

Pressing the A/C button only toggles the light on the button. I has no
effect on the compressor, which remains engaged. That is, unless you're
driving a Canadian-spec car.

 

All it's doing is turning off the light on the switch. It doesn't affect
the A/C compressor.

That's exactly the point. What works great in Florida is less than ideal
in New Hampshire.

 

I can send you copies of more than 10 years worth of MPG data...

I never said it doesn't consume extra fuel, and actually said just the
opposite. However, you are talking about what a 10-15% reduction in
fuel mileage? I don't know what your Elantra yields normally so I'm
just estimating here.

In city driving, this amount of reduction is probably easily possible as
the AC consumes about the same amount of power per hour, regardless of
distance traveled. However, on the highway, this is a terribly high
figure. Then again, maybe Chrysler and GM have more efficient AC than
Hyundai. I know GM for years was the world leader in AC technology.

Actually, just the opposite is true. AC consumes roughly a constant
amount of power per unit time. At slow city speeds when the vehicle is
using less fuel per unit time, the AC consumption will be a much higher
percentage of the total.


Matt

 

Yes, I have noticed that my Sonata isn't very good at defrosting. Then
again, it isn't very good at heating in general. The interesting thing
is that both my 94 Chevy pickup and my 03 Dodge Grand Caravan have this
same "automatic" AC in the defrost position feature, and they both defog
and defrost exceptionally well. The Chevy is slower to start defrosting
as it has a much larger cast iron engine that takes a while to heat up,
but once warm it will make the water on the windshield turn to steam
when you stop at a light.

Personally, I think this is more of poor HVAC design on Hyundai's part,
than a poor idea in general.

Yes, I personally prefer to have more things manual than automatic,
which is why I drive a stick shift. However, I have become used to
having automatic timing advance, automatic mixture control and automatic
fuel injection for cold starts...


Matt

 

How about this.... Open the hood, and disconnect the connector for the AC
clutch for the winter. Not as easy as doing it from the dashboard, but
effective.