Just yesterday the dash showed -28 celcius and while driving it went up slowy into positive temp and thats when the ac started working. Now today i started the car it showed -40 and when to -25 quite rapidly (within 3 min) and then slowing start going to -11. What could be wrong, the temp sensor is not broken as i checked visually. Is there a coding issue or i need a new sensor ?

 

Damn it sounds pretty cold up in MI, Just the other day I heard there were still icebergs in the great lakes !

JK, sounds like your sensor has gone out. It will clearly cause those types of readings if it becomes disconnected or defective. It's in you front number, I believe on the left inside. You should see the wire going to it.