My question is this:

When you have your automatic air/heat working and you set the temperature to say, 76, is it that:

The system should blow out whatever temperature air it needs to to bring the temperature in the vehicle down or up to 76.


The system should blow out air from the vents that is exactly 76 degrees therefore eventually bringing the temperature in the cabin to 76.

Which should it be?

If it matters I have a 2004 Chevy Tahoe.


It will blow heat/cold out to get to the desired temperature, then reduce the fan. It won't spit out the exact air temp, but will get closer to it as the temp in the cabin gets to the desired temp. There is a blend door which can vary the heat/cold as needed to maintain the temp. This is how my '06 Silverado with auto temp control works. Other vehicle brands may work differently.

  • Thanks! So follow up question if I may. What if it is not on auto? So in my Tahoe, I have a left and right thermostat. If the left is set to 72, what happens? Does the left side blow 72 degree air? Or are there sensors on the left side and when the left side hits 72 it stops? – CRAIG Feb 6 '15 at 2:51
  • There are two sensors which splits the cab in half into the zones. I've always thought that the two zones would actually be fighting each other. Since there is only one fan, you get one speed. I'm not positive if there are separate blend doors which feed each side, but it would make sense. As each zone gets to its target temp, a door probably shuts down to slow the amount of air going to that side. Being as anal as I am, I always keep the temp the same on both sides. I figure it doesn't make sense for the two sides to be working against each other all the time. – Pᴀᴜʟsᴛᴇʀ2 Feb 6 '15 at 15:39

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