Weird behaviour with the inside blower fan

[WILL E]

It may have happened once or twice before but today it did it a few times.



I have the AC on full and recirc. The fan will shift from blowing out the vents to blowing out the defroster. The air is still cold. I tried a few other blend positions and the same thing happens, it goes to blowing out the defroster, stays there for a minute or so and then goes back to the desired setting.



Is the door vacuum controlled or electronic controlled?



I tried 'making it happen' by stomping on the gas but it had no effect. On my old cars, when I have this issue, the lack of vacuum at full throttle causes a similar behaviour.



Thanks!

 

[Doug Stewart]

Had the same thing happen to me last week it was a small grey vacuum hose that had broken. Spliced it and all is well.

 

[Richard McAlister]

If MDtrac solution doesn't work --,

I had same symptoms, replaced the vacuum check valve under the hood. Problem went away. I bought mine from Amazon - "Motorcraft YG360 Vacuum Checking Switch" cost $9. The connector on the black side was a little bigger than the original, but the rubber hose stretched to fit just fine. The part is directional, make sure it goes back on the same way the old one came off (black side toward engine). Mine was located under the hood on the passenger side of the engine near the firewall.



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[WILL E]

Wow, still using vacuum to control the doors! Thanks guys I will check it out.