How was it improperly installed? I've noticed that in my situation, the crackling has only happened once, when it was 90+ degrees outside and my A/C was on full tilt. Over the last few days, it hasn't returned - maybe it has something to do with the fact that I started pounding on the dash with my fist and may have "settled" something underneath. Part of me wants it to come back so I can track down what it is and the other half of me is content to never hear it again! Whatever the cause, it was quite alarming and didn't sound natural by any means.