Question about 2003 Mercury Grand Marquis
Need advise air works all the time but comes out vent ,then switches to defroster& floor ---help
Check for vacuum leaks under your hood. You probably have a loose, broken or damaged vacuum line. Be sure to check the one that goes to your vacuum pot as well. With your engine running, wiggle as many hoses around as you can see, and listen for a hissing sound.
Posted on Jun 17, 2009
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Posted on Jan 02, 2017
SOURCE: Vent control
You have a vacuum leak.Defrost is the default postion(no vacuum).
See if you can locate the small black vacuum line that goes inside the vehicle on the passenger side near the heater core. The trace it back,should see it going to a canister then to the intake manifold.Make sure it is not disconnected or broken somewhere.
Posted on Mar 02, 2009
Is it a new vehicle? I had a new vehicle that had the same problem. Answer was that the holes weren't punched out of the vent.
Posted on May 23, 2009
either a vacumn pipe is broken or the ends split so its not passing a vacumn to open the flaps,where they are and how to get to them i cant help because i have never worked on one as they are not here in spain.check the engine end first though .Look for some small rubber pipes running from the inlet manifold
Posted on May 30, 2009
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