Air re-circulation

Tiny
JANODI
  • MEMBER
  • 2015 CHEVROLET COLORADO
  • 3.6L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 22,000 MILES
We have a crew cap, short bed, Z71. When traveling and in traffic, we will push the air re-circulation button to keep out the exhaust from other vehicles. However, we have noticed that pushing the air re-circulation button does not stop the fumes from coming into the cabin (e.G. We can smell the diesel exhaust from the truck ahead).

Looking around on the internet it seems that since 2014 GM has limited the air inlet vent to 90% closed even when the air re-circulation button is pushed. Is this true?

Is there anything I can do to change this? I am not sure where the air inlet vent (and actuator are on this truck).

Thanks in advance,
Jim
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Saturday, June 17th, 2017 AT 1:32 PM

6 Replies

Tiny
HMAC300
  • EXPERT
Our manual says nothing about how far the actuator opens or closes it may in your manual if you have one. Try a reset though, pull HVAC fuse inside truck for sixty seconds with key on that should reset all of them and may fix your problem. See picture of location.
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Saturday, June 17th, 2017 AT 3:11 PM
Tiny
JANODI
  • MEMBER
Okay, I did a little more looking and here is what I found:

I took out the glove box and pulled out the cabin filter. I turned the key to enable the fan, but did not start the engine. Then I pressed the button to turn on the fan with Recirculate off. Through the cabin filter slot I could see the air inlet vent door (I had a flash light and mirror and also an fiber optic inspection camera). I now also know where the air inlet actuator is (on the left side of the housing).

Then I turned activated the recirculate button and saw the vent cover rotate up to cover the hole in the top of the housing to the outside air and expose the holes in housing to the cabin (it rotates a "hood" inside the housing for a vent cover). Any time I turned the fan off, the recirculate went off and the vent cover returned to the down position to block the cabin inlet and let in outside air from the air inlet pipe at the top of the housing (this makes sense).

With the fan on and the recirculate button pressed and lit, I did not see any openings to the outside air pathway. This seems to nix the rumor I had read about GM making the vents only close 90%. I was even able to reach around the side of the housing and put my fingers in the cabin inlet holes and feel the vent cover door completely covering the outside air inlet.

I still do not know why we smell other vehicle exhaust when in recirculate mode (we do not have a diesel so I know it is not us). Is it possible that running the fan too high with recirculate causes a low pressure area that draws in some outside air? The previous owner had passed power cables through the firewall for a stereo (on the driver's side). I have removed them and silicone chalked the holes.

The cabin air inlet holes are on the back (and back sides) of the housing where the cabin filter is. When the glove box is in, there is very little space to have the air drawn in from the cabin (there is even a plastic kick plate on the bottom which obstructs the airflow to the cabin air inlets). So it seems like there is a lot of negative air pressure near the firewall when recirculate is active. I think we will try leaving the bottom kick plate off, run the fan at low speed when we have recirculate active, and make sure we do not pack too many things on the passenger-side floor when traveling that could obstruct the air flow.

Am I on the right track?

Jim
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Saturday, June 17th, 2017 AT 4:49 PM
Tiny
HMAC300
  • EXPERT
Due to carbon monoxide there are vents inside the cabin and that is where you are picking up the smell larger pickups have two vents behind the cab between box and cab which you can see if you look from the side. Not sure about a Colorado as I have not worked on one in a long time, but they may have the same which with something like that you do not have much to do about it.
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Sunday, June 18th, 2017 AT 7:13 AM
Tiny
JANODI
  • MEMBER
Thank you. And thank you for the diagram in the last post!
Jim
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Sunday, June 18th, 2017 AT 10:10 AM
Tiny
SATURNTECH9
  • EXPERT
Just to add to this one without some air coming in from outside you would lose cocisness not good.
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Sunday, June 18th, 2017 AT 2:28 PM
Tiny
JANODI
  • MEMBER
I'm aware of that. It's just for short periods of time where we try to avoid fumes.
Thanks
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Sunday, June 18th, 2017 AT 3:12 PM

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