Model X

Why is climate control on auto so schizophrenic?

I live in the San Francisco Bay Area. It is very common to drive from 80 degree weather just outside the city to 65 degree weather once I'm in the cold, foggy city.

I leave my MX climate control on Auto at all times and I tend to keep my temperature on 68-70 degrees.

I've noticed that when I drive from a hot to cold area that the car will suddenly start heating the interior. In the opposite direction, going from cold to hot, the car's climate control will immediately start blowing cold air.

The interior temperature does not change that quickly to warrant these annoying changes in the climate control and I find I have to constantly be adjusting the temperature.

My typical day driving the MX around is like "Why in the heck is my car heater on? Oops, looks like I just drove over the bridge and the external temp has dropped 20 degrees... time to F around with the climate control temperature to find the optimal temperature!"

Does anyone know why the car does this? I would think a climate control system would measure the interior temperature of the car. However, judging from what is happening, it seems to be measuring the external temperature or perhaps the temperature of the air coming into the car.

Thanks for any help to understand this "feature" of my car.


  • Check the app to see what internal temp the car is reporting. If it seems about right, it could be corrupted code not providing enough hysteresis around the setpoint. If it if clearly off, it is probably a bad thermistor inside the car.
  • To maintain the temperature inside the vehicle, the system will bring in outside air that has to be "conditioned". If the outside air is hotter than the inside setting, it will have to be cooled. If the air outside is cooler, it will have to be heated even if the difference between inside and outside is small. You can try to turn on the "recirculate" setting which should depend much less on the outside temperature to see if that reduces the sudden changes from heat to cool.
  • I think the core problem is the climate control target temperature has a 1º range.

    If you could set your target to a wider range 68º - 70º, it could circulate plain air in between and you wouldn't have to continually counteract it. (I'd pick an even wider target range.)

    The phone app displays the (1º) happy in-between zone with white airflow arrows vs. red when heating or blue when cooling. (Why doesn't the Model 3 console show that info?)

    So you depart in 80º weather with A/C cooling you down to 70º. As soon as the outside air drops to 69º on the bridge to SF, the car starts heating you up to 70º! Yuk. And in reverse on the return trip or driving through a mountain pass.

    Auto mode takes control over the fan, vents, A/C, and recirc. I don't understand: **What does Auto aim to achieve via those controls?** It still has thermostatic regulation, and you can decide how much fan wind and noise to take.

    If the aim of Auto mode is to reach the goal temperature as fast as possible, then it'll blast you with cold or hot air each time the temperature goes above or below the target.

    Perhaps Auto also decides somehow when to defrost the windshield.

    In non-Auto mode you can at least disable A/C to get a half-open target temperature range like 70º+.
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