I was driving to work yesterday afternoon (I work shifts), closed all the windows and powered up the a/c. After a mile or two I noticed warm still coming through the vents and the air con light was on. I fiddled with buttons and dials , nothing. I gave up on it and nother mile or two further, suddenly , ice cold arctic polar air came gushing through???? I think it kicked in when I revved up the motor to get past a bus, have no clue what happened.