The moring in cold the heater on 4
 

At 7:15AM, when I go to school in college. I stop at the traffic light with all dense fogs on front window. Then I put 4 speeds for heater to removed all the dense fog. The sound say "BOOM!". Something wrong with the car with the heater on 4 speeds of A/C. I better to check it out the a/c. Maybe the frost on the engine are hard to warming up or the fan speeds.

Anyone know what the sound BOOM? from the heater on a/c to removed the fog windows.

I have no idea what is going on i don't think u can really detect anything unless u know shit about the A/C in the car. But my advice is just keep it on 3rd level.

ya know...mine made a strange thump today as well...then it started to make this fluttering whistle sound...