• Tiny
  • buff9464
  • 2004 Ford Expedition

Air Conditioning problem
2004 Ford Expedition V8 Two Wheel Drive Automatic 143257 miles

Here is what I know. I have a vacuum leak that is causing my ac to switch from vent ot defrost vent when I accerlerate. But I am also hearing a thumping noise in the rear ac that sounds like a vent or baffle that is not working properly. When I turn on the rear ac the noise is louder. This is probably a vacuum problem also. I caanot change the rear air flow, it is stuck in floor mode. Is there a way to stop that noise without doing the whole vacuum problem like disconect the vacuum, get it to rear vent mode only and leave it there till I get the vacuum fixed.


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have the same problem?
Friday, May 1st, 2009 AT 12:41 PM

1 Reply

  • Tiny
  • merlin2021
  • Expert
  • 17,587 posts

The thumping can be as simple as one of the a/c lines touching the car body some where, the system defaulting to defrost is a sign that you have a vacuum leak in the reserve tank, follow the black supply line under the hood, one comes from the engine vacuum port and the other end goes into the reserve tank then into the car, Get a can of spray throttle body cleaner and spray these parts under the hood, when the idle changes you found the leak.

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Saturday, May 2nd, 2009 AT 5:40 AM

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