2006 Tucson: question about defrost/defog

Discussion in 'Hyundai Tucson' started by cheg, Jan 31, 2006.

  1. cheg

    cheg Guest


    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

    cheg, Jan 31, 2006
  2. cheg

    James Guest

    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.
    James, Jan 31, 2006
  3. 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.
    Brian Nystrom, Jan 31, 2006
  4. cheg

    Matt Whiting Guest

    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 Whiting, Jan 31, 2006
  5. cheg

    Don Allen Guest

    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

    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.
    Don Allen, Jan 31, 2006
  6. cheg

    cheg Guest

    *** 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!

    cheg, Jan 31, 2006
  7. 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 .....
    Victor A. Garcia, Jan 31, 2006
  8. cheg

    Pete & Cindy Guest

    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 & Cindy, Jan 31, 2006
  9. cheg

    Pete & Cindy Guest

    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 & Cindy, Jan 31, 2006
  10. cheg

    Matt Whiting Guest

    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 Whiting, Jan 31, 2006
  11. cheg

    JPH Guest

    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.

    JPH, Jan 31, 2006
  12. 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.
    Brian Nystrom, Feb 1, 2006
  13. 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.
    Brian Nystrom, Feb 1, 2006
  14. 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.
    Brian Nystrom, Feb 1, 2006
  15. 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.
    Brian Nystrom, Feb 1, 2006
  16. 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.
    Brian Nystrom, Feb 1, 2006
  17. 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.
    Brian Nystrom, Feb 1, 2006
  18. cheg

    Matt Whiting Guest

    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 Whiting, Feb 1, 2006
  19. cheg

    Matt Whiting Guest

    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 Whiting, Feb 1, 2006
  20. cheg

    Bob Guest

    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
    Bob, Feb 1, 2006
Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.