The a/c recirculated air door is not closed and brings in outdoor exhaust. What activates this door to close.

If exhaust is getting anywhere near any part of the HVAC induction system, you have a different problem to fix. Even on full recirc it doesn't seal 100%. If you're smelling exhaust, exhaust is coming out somewhere improper . . . or the vehicle is running inside a confined space, reversing at just the right speed and ambient conditions, or is driving with the rear doors open.

Perhaps you can expand on the situation?

I think he means outside air as exhaust.
The actuator is problematic.

Hopefully he comes back and lets us help him some more.

The outside exhaust we smell is from other cars on the interstate, not our suburban. The A/C is not very cold in the front and when I push the recirculating button I do not hear the door open or close. The rear air is cold and we found this year 1999, doesn't have a cabin air filter. What would cause the front a/c vents less cold than the rear?
Thank you for your help, this is my first time using the GM forum.

I saw a video of replacing the control panel and the recirculate air door button can be replaced with a $250 new one on Amazon. With 236,000 miles, I was hoping for a less cost approach. Can I close the outside air door/intake of this A/c unit. Thank You

Sounds like the blend door is getting hung up. If it allows heat into process it will not be all the way cold, even if the evaporator is all the way cold.