Have a 2007 Pontiac Grand Prix. The AC quit
working. At first it would pop on and off
from time to time. Then it would go off and
stay off for long periods, then just pop back
on. Now it's off and stays that way.
And what the heck is a knock sensor? Is it
AC: if it's low on refrigerant (r134a) the compressor will cycle on and off. When if finally gets too low it will just stay off and you will not have any AC. So take it somewhere and get it checked for leaks and r134a pressure. Knock sensor: yes this is important, and a trigger from the knock sensor can shut down the motor to prevent damage to itself. A missing knock sensor signal can also prevent an engine from starting.