Automatic Climate Control - temperature control (both sides) has little effect

[AbsoluteZero]

Driving in some cooler, high country, weather the past few days I noticed both driver and passenger side temperature controls had little effect on the discharge air temperature. Stayed cold both sides even when set in the upper 80's. I haven't had much time with three "active" grandkids onboard, to do much actual troubleshooting. Since both sides seemed to be effected I've initially discounted the temperature servo since it's not likely both sides would fail at the same time.
What little reading I've done suggests if one of the five interior sensors (thermistors) were faulty the system goes into a default mode and tries to deliver air at a near comfortable level.
Running a calibration.... pulling fuse 36 had no effect.
As best as I can determine the automatic control does what it's supposed to. Blower speeds can be varied. Recirc works.
Have any forum members experienced this situation/failure?

 

[The_Roadie]

I don't recall anyone ever having that exact problem and posting up about it. A GM Tech II tool can read each of the sensors and confirm your theory, which I think is a good one. You should also feel the temp of the hot water hose running through the the firewall to the heater core. If that flow is too low (low coolant level or collapsed hose) that's another possible cause.