AC door actuator was bad making clicking noise a few months ago. I was lazy,didn't fix it, just disconnected the electrical connector inside the center console. Last week I noticed the mileage started to go down gradually, eventually stayed at about 12MPG. I was really puzzled after checking a lot of things had no idea what had went wrong. Today I turned off the ac, reset the meter went out for a while now the mileage went up to 21 MPG. Now I know the problem is related to the AC, but how can the AC make such a big difference? Do you guys have any idea? Any input will be greatly appreciated.