The GFs 96 S10 is the vehicle in question. I hardly ever drive it so I'll take her word on the fact that the heat is still coming into the cabin with the controller set to off. The heat works great since I finally got all the Dex glug out of the system, but it's starting to get warm and I don't want an ear ache. Could it be something as simple as the heater / AC control cluster? I also have to chase down a leak in the AC system but need to kill the heat first. TIA from an old guy

Check all vacuum to and from heater controls.