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MY 2009 E-150 XLT HAS A HIGH PITCHED INTERMITTENT SQUEAL THAT ONLY LASTS FOR A SECOND OR TWO THEN GOES AWAY , ONLY WHEN THE A/C IS ON. IT COMES FROM THE DASH OR IT WILL BE HEARD IN THE REAR AIR UNIT. I HEAR IT MORE WHEN I'M IN STOP AND GO TRAFFIC, BUT IT CAN BE HEARD AT ANY TIME. IT DOESN'T MATTER IF IT'S IN NORMAL OR MAX A/C, BUT I HAVE ONLY HEARD IT WHEN THE A/C IS ON. THE BEST WAY TO DESCRIBE IT IS IT'S LIKE A SQUEAKY DOOR OPENING OR A VACCUUM SQUEAL. I HAVE TALKED TO MY CO WORKERS AND THEY HAVE HEARD SIMILAR SOUNDS IN THEIR FORDS. IT MUST NOT BE UNCOMMON, BUT MINE IS DOING IT ALOT, AND DRIVING ME CRAZY. I WANT TO HAVE SOME IDEA WHAT TO TELL THE DEALER WHAT IT IS . ANYONE HAVE A CLUE ???