I have owned Buicks all my life with ATC. Set it at one temperature year round and forget it. However with my new TCH I am having a problem. When it is warm outside I set it at 71 and the A/C is fine. The next morning when it is cold outside it gets so hot inside the car I have to turn it down to 68 or 69 so it won't be roasting inside. Why can't you set the temperature and it stay the same whether the A/C is on or Heat?

 

Cause it's trying to get to the temperature asap. If you set 71 on a cool summer's night and you didn't drive til the middle of the next day and it was 90 outside, it'll blast the A/C as well.

 

It may "BLAST" but it will stop at the desired temperature. The heat continues on well PAST the set temperature so you have to lower the temperature setting to get it to stop. When it warms up outside then the AC gets too cold and you have to raise the temperature back up again.

I never had this problem with ATC before.

 

Most likely it's due to the location of the temperature sensor.

The temp most likely does go well past the desired temp at head height but that hot air has to come down to the level of the thermostat in order to turn it off.

 

The TCH also has a sunlight sensor on the dash, that will increase (or decrease) the cooling based on amount of sunlight it senses. If I place a piece of paper over the sensor, fooling it into thinking it is a shady day, the fan speed will drop several notches, which in turn will slow down "over shooting" of the desired temp setting.

 

I have this same problem. I got a small digital thermometer just to check how far it over shoot. With the control set to 72 it will heat the car up to about 78 before it starts to slow down the fans. I have move my thermometer from the dash to the seat the center console. It always over shoots by 5 to 6 degrees.

 

I wonder if there is a relationship between the airflow amount and direction (the settings on the vents themselves). If a 'critical' vent is turned off or toward a direction that causes a 'dead spot' in the air flow, would this be the result? SWMBO has a tendency to do these things, and it tends to cause problems like this.

Just a suggestion.

 

About the climate control, why does the AC always turn on with automatic climate control even if it is very cold out and the heat is on?

 

"Why does the AC always turn on...."

Because some idiot(s) at NipponDenso in Japan, or the US counterpart, Denso US, thought it would be a good idea to run the A/C during the wintertime to help in dehumidifying the incoming airflow and thereby prevent windshield fogging.

For many years I simply disconnected or somehow disabled the A/C compressor during the winter months. Some newer Denso designed systems have the ability, dealer only parameter set, to allow you to disable the A/C indefinitely.

Running the A/C for dehumidification is a total wild card, functionality depending strictly on the welms of mother nature, and we all know just how fickle she might be. Additionally there are HAZARDS associated with this, also dependent of mother nature.

Experienced episodes of sudden windshield fogging...??

 

There are two parts, aspects, to the human comfort equation, surrounding air temperature is often only about half of the equation, the temperature of the surrounding "landscape" and interior surfaces can sometimes rise to more that half.

Automotive engineers, seemingly, have only recently become aware of this, the radiant heating/cooling effects on the human body. So the idea, probably, is to heat the interior surfaces up quickly as an aid to human comfort.