2005 Elantra A/C light

In winter the Temperature Control is at "warm" (red zone), while turn the Fan Speed Control from "0" to "1", the A/C light always turns on. Why? (I
thought the A/C is for cooling only)
Anyone has my situations?
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Two possible reasons: 1. The a/c was left on. 2. The mode switch is set to defrost. A/C will greatly improve defroster efficiency.
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Yes, these two are the expected cause of what he described. But, at least in my case, it happened even when those two above conditions did not occur. My dealer called it an anomoly, and to be honest, it wasn't a big enough issue for me personally to push it to the next level with Hyundai.
After a short time I just learned to automatically turn off the A/C every time I turned on the fan. And to make it worse, it didn't happen every single time, but did happen more times than not.
Eric
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hyundaitech wrote:

"Defogger" yes, "defroster" no.
The A/C dehumidifies that air coming through the vents, which does help to remove MOISTURE from the INSIDE of the windshield. OTOH, if you have snow/ice/frost on the OUTSIDE of the windshield, having the A/C on REDUCES the system's ability to melt it, since it lowers the temperature of the air coming through the vents and increases the the time it takes for the air to get warm. In the winter, it just plain sucks!
Unfortunately, '01 and up US-spec Elantras have this dubious "feature" built in. On '01-'03 cars, snipping a single wire allows for completely independent A/C control, using the A/C switch. On '05 and up Elantras, the new control module prevents that simple modification. That's why I installed a switch in the A/C line that allows me to manually turn off the compressor when I need maximum efficiency from the defroster or when I prefer to clear fog from the windshield with heat, rather than cool, dry air. It also increases my gas mileage when using the defroster.
BTW, when the heater control is set to defog/defrost, the A/C button is bypassed. Although pushing it will turn the light on and off, the compressor runs regardless. Interestingly, on Canadian-spec cars, the A/C switch CAN be used to turn the compressor on and of in defog/defrost mode.
I have heard that this stupid system is now mandated by the DOT for all cars sold in the US that are equipped with A/C. Considering that it was something that could be done manually when necessary, it seems like a step backward and just another pointless attempt to idiot-proof cars.
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Actually, the system is smarter than you might think. There's a temperature sensor on the evaporator that inhibits the compressor when the evaporator is close to 0 degrees C. If it's close enough to freezing outside that you have ice or snow on the windshield, then the compressor is not likely to be running. Even if it is, the temperature difference as a result of it running is pretty small. All you are trying to do to melt the ice / frost is to get the temp. of the glass a little above freezing - that's while you are still parked. After you are moving, and if the temp. of the air passing over the evaporator is warm enough, the fact that the air is dried helps keep the inside of the windshield clear.
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Bob wrote:

On would think that would be the case, but you can feel the compressor kick in and feel the temp difference in the air.

The problems is that it's NOT just an issue when you're sitting still. Last winter, I got caught in a situation where I couldn't keep freezing drizzle off the windshield, even with the heat set and fan set to max with the defroster on. The temp wasn't much below freezing at the time. I've never had that problem in a car before.

Heat keeps the inside of the windshield clear quite effectively unless we've just come in from some sweaty activity like X/C skiing. If I need the A/C to reduce humidity in the car, I can turn it on myself.
The point is that this should be an option that's controlled by the driver, not something that's imposed by the heater control module.
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    I agree with you Brian, this feature drives me nuts. It's only under extreme conditions that you would want to kick the A/C on in order to help with removing the moisture from the inside of the windshield.     This was also added I believe in part to people not turning on their A/C in the winter time and causing the seals in the A/C system to crack and ruin the system. My Acura Integra doesn't have this feature and I usually turn the A/C on once a month and have never had any problems with the system for 11 years now.     My mother's 99 Accord had this stupid feature, luckily Honda had built in a feature to enable and disable it (Not sure if the current generation Accord have the ability to turn it off).
Nick
wrote:

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almost all cars now turn the ac on when in defrost mode, some just do not turn on the ac light...

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Nick wrote:

The other thing that I hate about it is that if you put on the defroster to clear the windshield, then switch to heat to warm up the rest of the car, the moisture on the condenser gets pumped into the car, causing everything to fog up again. That's why I prefer to use heat to keep the inside of the windows clear whenever possible.

That could be. This is the first car I've owned with A/C and I rarely use it, largely because of the gas mileage penalty of using it. I find the system to be far stronger than it needs to be and I wisk there was a way to install an under-drive pulley to reduce the drag on the engine when it's running.
One thing that a lot of Elantra owners have learned the hard way is that the A/C heat exchanger is mounted in a position where it's vulnerable to damage from stones and other debris kicked up from the road. Like many, I've added screen behind the grill to prevent damage.

My understanding is the automatic system is DOT mandated for '05 and newer vehicles.
For anyone interested in learning more about these and other issues and modifications to the Elantra, the Elantra Club Website is a treasure trove of knowledge. http://elantragtclub.tripod.com/elantra /

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I had the same thing happen to me on my 2003 Elantra. It happened for the 3 years I owned the car. The dealer had no clue how to fix it, but acknowledged that it was a legitimate problem, and mine was the only car they had seen it on. We never found a fix.
Sorry I can't help more, but at least you know you are not the only one.
Eric
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Eric G. wrote:

Is the control on the Elantra anything like the new Sonata? I've found my AC turned on several times, but I'm pretty sure it is because I hit the center button inadvertantly while grabbing the dial to change the fan speed. The button takes almost no force to push the AC on and I think I'm just grazing it with my finger as I reach for the speed control. Having it in the center of the speed control knob and having it take such little force to actuate is not a smart design.
Is there any chance of this happening on your Elantra or is the control completely different from the 06 Sonata?
Matt
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No, it's a completely seperate button on the Elantra, detached from the fan speed control. And I have done the same on the new Sonata.
Don't worry, the dealer thought I was nuts too. In fact the service manager didn't even believe the first tech that reproduced it.
The really weird thing is that it seemed to happen even more often as the temperature dropped.
Eric
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Eric G. wrote:

I don't think you are nuts, I was just looking for any possible explanation. I thought something was wrong with my Sonata at first, but then decided it was my finger hitting the button inadvertantly. Sounds like this isn't a possibility on your Elantra.
Matt
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I wasn't exactly claiming that you were calling me nuts. I really thought it was something I was doing wrong. Even with the button seperate, it is potentially close enough that a finger could hit it while in the neighborhood. I swear I spent months trying to make sure I didn't do it before I brought it to the dealer and complained. And there were times (like maybe for a week) that it didn't happen at all. It was very non-linear as to when or why it happened.
Eric
P.S. - I have since traded that car in for my 2006 Sonata. My wife still drives her 2002 Elantra and this has never happened in that car.
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