Vented Fresh Air is Much Warmer than Outside Air?

laketboy · January 10, 2017

Read posts on "Climate Control" and "Recirculate let's outside air and smells in", but didn't find anything similar to what I'm seeing with my new 2016 Silverado 5.3L LS Double Cab. I've noticed this: With fan on and Temp all the way on Cold/Blue, A/C (light) off and Recirclate (light) OFF, I get air that is much warmer coming through vents than outside air. Today was mid-70's here in Dallas area. Window down, outside air fresh and comfortable. "Fresh Air" coming through dash vents was much warmer. Noticed same thing on much cooler day. One day in the 50's it was too cool to have windows down and too warm to have vent off or fresh air vent open. Had to turn A/C on low.

Anyone else seeing this on their new gen GM truck?

newdude · January 10, 2017

Normal.

With the AC off and recirculation off, it is taking air from the fresh air cowl duct, and passing it through the HVAC case. The case houses both the evaporator and the heater core. So, even if you set the temp to cold, and the temp doors go to cold, it is still getting warmth from the heater core (which flows engine coolant through it). Plus, you are taking the ambient air and its getting heated passing through the cowl which isn't far off from the engine bay itself.

If you want cooler air but a warmer temp, you'd have to turn the AC on. Max cold would be with recirculation ON as it would take the cold air in the cabin and then cool it even further.

mjoekingz28 · January 10, 2017

Good explanation!

laketboy · January 10, 2017

Thanks 15H, that makes sense. I know a lot has changed in 16 years (2000 Silverado) AND at times we think "I'm sure this worked/felt different on other vehicle(s). Pretty sure with same control settings, my 2000 Silverado had much fresher air coming in vents. I knew coolant was always running through heater core and LONG ago apprenticed on Chevy auto HVAC so remember the evap coil/core is conducting/absorbing heat (I think, right?), so what you say know makes sense. BTW, I called local dealer service and asked and the service rep indicated that this would be normal as well. He suggested that I use Recirculate without A/C on to see if air coming through vents was cooler. I'll try that and update. Feeling comfortable that this is normal and that I don't have an issue with one of the HVAC vacuum doors not operating correctly. Thanks again!