I have a 2000 Hyundai Accent. Recently I noticed that whenever I turn the blower fan to the defrost (blow on windshield) or defrost/feet option, the air conditiong light turns on which makes me think the air conditioner is running (even though the button is not pushed in to manualy turn it on). Is this normal? I have never noticed it before. Also, when I have the blower fan on those settings, it seems like the car has less power (could be my imagination though). When I turn the switch to blow the air just on the feet or straight out at the passengers, the light goes off (but will go on if I push the air conditioner button) What can I do to test this? If I wanted to disconnect the air condiotioner for the winter, would that mess up any other sensors on the engine?

 

Yes that is normal operation on most, if not all modern vehicles. It purpose is to dehumidify the air, speeding up the defrost process. Additionally, you used to need to run your AC at regular intervals so your compressor shaft seal didn't dry out, causing a leak. Since most of us failed to remember to do that, there is the additional benefit of regular winter operation of your compressor, keeping the seal lubricated and hopefully, leak free.

 

It's perfectly normal. If you have your fan on ANY defrost setting, the AC compressor will run. If you want to disconnect the AC, the only way is to unplug the connector going into the unit (power cut off) and in some cases if you look under your hood above the rad there should be a diagram of the belt drive system. Generally, there's a diagram with AC connected, and with no AC connected. Another option is when the compressor becomes inoperable you can unbolt the unit and remove it (unless you want it replaced/rebuilt), as it'll save 20+lbs of dead weight under the hood. If you disconnect the power to the unit don't be alarmed if a "check engine" or "service engine soon" warning lights up on your dash. The PCM doesn't always know what we humans are up to at times. AC compressors will rob you of 5-20hp depending on how hard the unit's working and engine size/configuration.

When all else fails just leave your fan setting on anything that doesn't have a defrost diagram attached to it and the compressor will not run. I recommend that defrost is only used in early cool mornings for a short while until the vehicle warms, then change the setting to say "floor" where it'll save you some liquid gold!