Air Conditioner unit will not shut off
#1

I have a Payne Air Conitioner and at 10:00 pm last night we shut it off using the wall thermostat. It never shut off. I had to turn off the power and unplug the unit in order to stop it from running. Why is it doing this?? The unit is approx. 5 years old.

#2
either
24 volt contactor at o/d unit...where the power wires from the house terminate inside the a/c, or thermostat, my guess, contactor. remove "Y" wire from tstat after removing power, if still hapens, contactor, if not tstat is culprit