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A/C will blow out defrost

Tiny
MICHAELDV
  • MEMBER
  • 2001 LINCOLN CONTINENTAL
  • 1,770,160 MILES
When it gets 90% outside the A/C will start blowing out the defrost, it still blows cold. Does it more when light on the gas when I have to down shift to clime hill it works fine. I changed the check valve and tested the vacuum can and it holds. Is there something that I missing?
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Thursday, August 6th, 2020 AT 7:20 PM

3 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good morning,

This sounds like a vacuum issue.

https://www.2carpros.com/articles/air-vents-stay-in-the-defrost-position

I attached a flow chart for you below to do the testing. If all the vacuum system checks out, the control head is going to be the issue.

Roy
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Friday, August 7th, 2020 AT 4:43 AM
Tiny
MICHAELDV
  • MEMBER
  • 11 POSTS
You know it's hard enough to fix this car but when you get a bad brand new part makes you go crazy. I guess that's why I don't have much hair left. I found that the check valve was bad. I had to wait for a hot day and hot engine to find the that the valve is bad. I really do not like working on car that are hot to find the problems.
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Friday, August 7th, 2020 AT 9:48 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good find.

I agree. You always assume the new part is good.

Roy
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Friday, August 7th, 2020 AT 9:55 AM

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