I had a car once were the air temperature control got stuck on heat, no matter what position it was in from cold to hot. It might be as simple as a vacuum hose came loose or developed a leak or the actual controller might have failed.I have a 2006 Sonata GLS that with or without the AC on still blows hot air through the vents at all times. I have 110k miles on the car and it will not be covered so just trying to see what it could be myself before bringing it into a shop.
How do you turn the heat off, by adjusting the air temperature control. All it does is control how much outside/cabin/AC air is taken in versus air that has been heated by heater core. If that is stuck on heat then no matter what you do, heat will always come out of whatever vents you have selected, regardless of whether or not the AC is on.The hot air comes through even with the AC and heat off.
Not necessarily, if the air temperature control is stuck on heat, then running the AC with the temperature control on the coldest setting will still produce heat and does not mean the AC is not working, since the air will be coming from the heater core, not from the AC even though it is running. Also, I've never had the outside air temperature feel as hot as when the heat is fully on, even when it is hot outside, which can reach over 100 degrees at times. In fact, I rarely use AC during in town driving to lessen load on engine, save gas, etc. and the vent air has at best been warm, never hot. The movement of the air does cool it slightly and may feel warm but not hot like when the heat is on.Either way, if you have your AC on, and the temp. control is at the coldest -- your AC system is not working properly. Test A. tells you the AC is shot and doing nothing. Test B. tells you your HEATER is stuck on the ON position, even though your AC might be functioning OK....
As 2 independent tests, you are correct. I, mistakenly, read into your post that these test were run consecutively, and was pointing out that test B was inconclusive until heating system was working properly again. My apologies.I actually EDITED my text after I posted it, but still BEFORE you posted yours... Yes, as you can read on my edited text, the AC could be functioning, while the HEATER is on.... This is actually what's happening in a cold winter, when you turn the defrost on to DRY the inside warm air, clear the windows from fogging. The air comes in warm -- but dry.
Using my 2 tests can distinguish better between a failing AC and a stuck HEATING system.