My girlfriend's 1998 Mercury Sable LS has climate control. You set the temperature and it decides whether to heat or cool the interior. Problem is, it is always running the AC. Even if I turn on it up to 90F, I can see the AC compressor kicking in and ice cold air is blowing out.
I've run the EATC self-test and and got code 024, so I tried replacing the blend door actuator, but during testing of the new part, it appeared the system didn't even attempt to move it.
This was her mother's car, and she was a heavy smoker. I noticed that the hose labeled "sensor" is almost completely clogged. Could this have something to do with it? I can't find anything only for "heat sensor" or "thermostat" that doesn't relate to the engine. And all the YouTube videos are about manual heating/cooling, and not the Climate Control system installed.
Lastly, could it be that the "head" unit has gone bad? Her niece had the car for the last month and had no complaints, we got it back last week and noticed the AC was stuck on.