New to me 2021 GLC. I usually set the cabin temp at 72 degrees, pretty consistent in my last 2 cars, a Lincoln and a Caddy. On the GLC I have to turn it up 2 or 3 degrees for it to be comfortable. Those big vents in the dash blow like crazy, so I'm wondering if the intent is to leave them fully open all the time or have to adjust them appropriately to keep it comfortable. Tried redirecting the airflow to my feet, but don't feel much airflow when I do that.

How do you use the system in your car?

 

Try just using the automatic setting, and aiming the vents.
The Automatic setting "decides" where the air is most needed, which changes as the car reaches its set temperature.
I only mess with manual direction if it's really humid and I need more defrost, but then only briefly.

 

I miss the simplicity of the 3 knob climate control system -- fan speed, temperature and zone. All adjustable without having to take eyes off driving to navigate through menus trying to decide if I'm a 74F guy or a 68F guy.

 

As long as you use the Auto setting, you only have one button. Up for warmer, down for cooler.
Trying to override the car 's algorithm, though, can take some concentration.

 

My 2020 GLC300 also is "too cold": here in Southern Arizona, I have to set it to 81 degrees to keep from being frozen in the summer. The dealer said something on the order of "deal with it". When outside temps are lower than inside, the problem does not occur.

 

Three....the insane woman in the right side of the car changes hers to be 8+ deg cooler, then turns on the rear AC even colder than that (there is not even anyone in the freaking back seat). THANK GOD I can turn off the zone with one button.

But, as to the OP. If I have mine at 72 and hers is at 65, I freeze....

 

Yeah, I think if there's more than four or five° difference between left and right settings, the whole system gets confused.

 

I also set the HVAC to 72 in pretty much every car I've ever owned with an automatic HVAC. During the summer if I have a lot of body heat stored, I turn it down to 70, sometimes 68, and/or use the seat ventilation. In the winter, which doesn't get very cold here, I occasionally turn on the seat heater at level 2 for a bit if the car has been sitting outside and the leather is cold. My 2019 C63 has pretty much the same interior setup and tech as your 2021 GLC. Same three center vents etc. Neither my wife nor I particularly like air being blown directly at us, unless I need to cool down after being out in the heat or exercising. So I have the two outside center vents closed most of the time and the one in the center blowing straight back. My wife keeps her vent by the door closed, and I have mine aimed up and towards the window so it creates sort of an air curtain between the glass and myself, but doesn't blow at me. Both zones are also synced.

Sometimes in the winter, my wife turns up her side, or just turns on the seat heater, which get pretty toasty. Multi zone climate controls in a car are basically wishful thinking. The air doesn't care about zones, so what you get is an average temperature with the air mixing between all the zones. There are some people who think they can outsmart the system by manually controlling the fan speed and directing the air, but it doesn't really work out. If you start messing with the fan and air direction, you knock it out of the automatic mode and it doesn't really work. Just leave it in Auto and it will do its thing, keeping the cabin at the desired temperature.

Granted the GLC has a larger cabin with a lot of dead space and an open cargo area compared to my C63 Coupe. That's all spaces that have to be heated and cooled, so it's likely not as efficient, but your best bet is still to let it do its thing. I've driven many loaners including the GLC at various times of the year and I keep all of them at 72. In my personal experience, 72 is 72 in all of them. Might be an issue with your specific car. There are several sensors that collect data for the HVAC. There are interior and exterior temperature sensors as well as ambient light sensors. The latter for example causes the system to cool more on a hot sunny day to compensate for the radiant heat from the direct sun light. So if you have your windows tinted for example, this can throw things off as the system is calibrated for the factory tint of the glass.

 

Thanks all for the responses. To add fuel to the fire, I tried adjusting the airflow to be to feet only using the dash controls. I felt nothing! When I turned the fan speed up all the way I felt a little trickle of cold air but not the blast I was expecting. I don't know the car that well to know if this is "normal." I'm going to check with my "concierge" at the dealer, but if you have the chance, try that with your cars and tell me the result.