My mother-in-law bought this Envoy new and it has proven to be a great vehicle for her. About a year ago her battery went dead and when changed the auto controls for the dash are stuck on defrost. Here is Al that is not very comfortable and she has asked if I can look at it. I have researched that there is a mode control valve that goes through a calibration whenever it looses power i.e. changing the vehicle battery but not at every start-up supposedly. It is supposedly very common for it to stick when it hits one of the stops and then you have the condition of defrost only. Most mechanics on-line are suggesting replacement of this part which is not too expensive. I have not crawled under the dash for this yet but is it possible to reset this mode controller, I’m guessing its a stepper motor, start the learn process and try not to let it get stuck on the stops to finish the calibration instead of replacing the thing? This repair at a shop is easily $275+ and sounds like GM should be slapped for something like this. Maybe it is in the owner’s manual, a correct procedure for replacing the battery but if it is dead when you get up in the morning you aren’t going to be able to follow a proper procedure.
This is the problem: