Air Conditioning issue on 1999 Ford F-250 Super Duty

A/C stopped blowing through front dash vents during long drive. Cold air is now blowing out of the defrost vents. Ever heard of this issue? How to fix?

by in Waxhaw, NC on August 25, 2010
4 answers 4 comments
ANSWER by on August 25, 2010
possible vacuum pump failure.a loss of vacuum will cause air to blow out of defrost vents,and vacuum pumps fail all of the time.
COMMENT by on August 30, 2010
THE ISSUE WAS LOSS OF VACUUM, BUT NOT DUE TO FAILED VACUUM PUMP. THE PROBLEM WAS SIMPLY A VACUUM LINE CONNECTOR/UNION THAT HAD BEEN KICKED APART BY MY WEEKEND PASSENGER WHO HAD JUST HAD SURGERY ON HIS FOOT - SO HE HAD HAPPY FEET! THANKS FOR YOUR ANSWER!
COMMENT by on September 09, 2010
good!I love cheap fixes!
ANSWER by on August 25, 2010
You lost the vacume to the controle unit. It a black or grey vacume line going from the firewall to the intake manifold is where they break most of the time. Check that first.
COMMENT by on August 30, 2010
YOU ARE ABSOLUTELY RIGHT. THE PROBLEM WAS LOSS OF VACUUM ON THE SYSTEM. ONE OF MY BUDDIES THAT CAN FIX ANYTHING LOOKED OVER THE SITUATION FOR ABOUT 5-MINUTES. AFTER LOCATING THE "CONTROL UNIT" AS YOU CALL IT (VACUUM IN THIS BOX) WE FOLLOWED THE VACUUM LINE THROUGH THE FIREWALL UNDERNEATH THE DASH WHERE ANY PASSENGERS WOULD PUT THEIR FEET. THERE WE FOUND THE "DISCONNECT." APPARENTLY, MY PASSENGER ON THE WEEKEND HAD KICKED-APART THE CONNECTOR UNDER THE DASH THAT THE VACUUM LINE RUNS INTO AND OUT. AFTER RECONNECTING, A/C BLOWS OUT THE FRONT VENTS NOW. THANKS FOR YOUR ANSWER - IT CERTAINLY GOT ME LOOKING IN THE RIGHT DIRECTION. IT'S FIXED, AND I SAVED A TON OF MONEY. FUNNY THING, WE HAVE AN OLD "98 DODGE RAM 1500 PICK-UP AT THE PAPERMILL THAT IS NOW BLOWING A/C OUT THE DEFROST VENTS. I CHECKED UNDER THE HOOD - THE VACUUM LINE IS SEPARATED, SO I KNOW HOW TO FIX BECAUSE OF THE ISSUE WITH MY F250. THANKS!
COMMENT by on September 05, 2010
Hello I read this answer and I thinkind can apply this to my SUV 1995 blazer 4x4 LT, I have the same trouble, how I can find the Vacuum connector? Thank you very much in advance
ANSWER by on September 05, 2010
I recenlty had this happen in my 2001 Cadillac Deville. The A/C wouild only blow through the defrost and floor vents. The cause was a "binding actuator" I took it to the dealer,and the charge was around $495.00.
ANSWER by on October 12, 2010
I have a 99 Yukon. It would blow either hot or cold air out of the defrost and floor vents just fine. When switched to blow out the main vents it would sound like it was blowing full blast but only a trickle of air would come out. I heard that sometimes the "blending door"gets stuck. I used the Fonzi-technique and with a rubber mallet (Okay, actually I used my kid's cow flash light that moos every time you turn it on), and beat on the front and driver side of the black plastic box located between the controls and the hump of the floor. (It is the black box that has the center floor vents coming out of it.) It worked and unstuck the door. Now I can switch from defrost to main to floor vents without any problems...
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