2002 Expedition Air Cond issue - AC Auto Repair Help Forum


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2002 Expedition Air Cond issue

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pspjim
New User

Nov 19, 2009, 3:31 PM

Post #1 of 4 (1859 views)

2002 Expedition Air Cond issue	Sign In

My Expedition Air Cond changes from dash vents to defrost vents on its own, then it changes back in a couple of minutes, this goes back and forth as long as the air is on.....
I have not tried anything yet. I'm not sure if this an electrical issue or vacuum issue?

Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Nov 19, 2009, 4:04 PM

Post #2 of 4 (1854 views)

Re: 2002 Expedition Air Cond issue	Sign In

The mode selection is done through a series of air doors that are operated by vacuum. When there is either a partial or total loss of vacuum, the system will default to either defrost or on some vehicles, heat. Acceleration can also have an effect on the doors for the same reason.

Look under the hood for a small black plastic hose coming through the firewall. Follow it to the vacuum source looking for any breaks, cracks or leaks. Also follow any other lines that branch off because they may go to a vacuum reservoir (storage tank) and a leak there will cause the same problem. Using a vacuum gauge to determine if you have full vacuum at any given point is the best way to find it. You can cut into the line anywhere and splice it back together with a piece of vacuum hose. Find the broken line, you found your problem.

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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.

pspjim
New User

Nov 19, 2009, 6:21 PM

Post #3 of 4 (1849 views)

Re: 2002 Expedition Air Cond issue	Sign In

Thanks, I will do that, I suspected it might be vacuum controlled

Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Nov 20, 2009, 12:27 PM

Post #4 of 4 (1843 views)

Re: 2002 Expedition Air Cond issue	Sign In

Hammer would have more data than I but that was classic for a vacuum leak/issue as he said. Some may be using plastic for part of the line - gets brittle like pasta - if the case just use rubber hose for auto use and it works fine. Unsaid in this post - the put a bunch of stuff the can be pulled apart just to check trans fluid in my fav cars! Nothing out there is perfect, - well except my 1963 Falcon! Young once (clock ticks for all of us) and rolled it over and still drove that thing home! Was resting on side and had to put it back but sucker still ran right!

T

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