HVAC - Is this normal?
Thread Starter
Instructor
Joined: Jul 2006
Posts: 141
Likes: 0
From: New York
HVAC - Is this normal?
I have auto HVAC on my 98. Drove to work this AM and the outside temp read 43 degrees. All the way to work, regardless of me changing the interior temp from 68 - 80 the A/C light stayed on (no blinking just on). As I moved the interior temp around I watched the vents change from defrost to under the dash..still no change. The heat works perfectly. The temp was great and fan speed was responding great to the temp as I moved it around. Any ideas?
Tech Contributor
Joined: Dec 2006
Posts: 10,962
Likes: 29
From: Van Buren Arkansas
Wounded Warrior Escort '11
The system looks at a combination of sensors such as the outside and the inside temperature to determine how much heat and how much cooling is needed to keep the inside at the selected temperatures. Yes, it runs both the heating and cooling simultaneously to do this. The compressor will shut off when the BCM commands it to do so and that usually happens between 38 and 43 degrees F, outside temps. I will venture a pure guess here that its software decision process is based upon temperature changes over a short amount of time and if the two temperatures (Inside and Outside) remain stable or not.
Safety Car
Joined: Aug 2000
Posts: 4,933
Likes: 30
From: San Rafael CA
RTFM ....
Your A/C will be on any time the system is set to AUTO unless the outside temperature is between 35 to 40 degrees. If the outside temp is below the minimum amount, the A/C button will flash if you attempt to engage A/C in MANUAL mode.
The HVAC controller uses the A/C system to de-humidfy the air before warming it and sending it into the vehicle cabin. This reduces the chances of the windows fogging on a cold morning.
The GM HVAC system is considered one of the best in the world. You almost never see an auto magazine even mention it because it is so good it goes virtually unnoticed. Put in AUTO mode, set the temp you want, and enjoy what it can do for you. The software behind it is quite sophisticated, even with features such as when the HVAC controller requests the A/C compressor ON, the PCM (which actually controls the compressor) throttles the engine up slightly at compressor engagement to minimize the feeling you get in many cars of a hesitation in engine power as the compressor comes on line.
Your A/C will be on any time the system is set to AUTO unless the outside temperature is between 35 to 40 degrees. If the outside temp is below the minimum amount, the A/C button will flash if you attempt to engage A/C in MANUAL mode.
The HVAC controller uses the A/C system to de-humidfy the air before warming it and sending it into the vehicle cabin. This reduces the chances of the windows fogging on a cold morning.
The GM HVAC system is considered one of the best in the world. You almost never see an auto magazine even mention it because it is so good it goes virtually unnoticed. Put in AUTO mode, set the temp you want, and enjoy what it can do for you. The software behind it is quite sophisticated, even with features such as when the HVAC controller requests the A/C compressor ON, the PCM (which actually controls the compressor) throttles the engine up slightly at compressor engagement to minimize the feeling you get in many cars of a hesitation in engine power as the compressor comes on line.
Thread Starter
Instructor
Joined: Jul 2006
Posts: 141
Likes: 0
From: New York
Amazing. Thanks a lot! Love it when you think something is broken to find out it is superior. Makes sense because I read a few other posts which talked about removing humidity. Appreciate all the feedback.
