Tip & How-To about Ford Crown Victoria

Electronic Hater/A/C Controls Blows out Defrost Ducts - Frod, Lincoln, Mercury

A poorly fitting vacuum harness to the control head results in vacuum leaking and air blows out the defrost ducts by default by law.

You can replace the vacuum harness or use two 10" tie straps that wrap around the back plate and go on either side of the black vacuum supply hose. I have photos I can send out if needed.
The vacuum harness is $22, but even if you replace it, you should use the tie straps. There is not enough of an interference fit bweteen the hoses and the tubes.

You also may have internal vacuum leaks on the control head back/bottom plate. It has 4 solenoids that direct vacuum to the correct vacuum motor on the plenum. Thy have been known to leak.

Gino on Ebay fixes them on an exchange basis for about $125.

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2 Answers

my ac only blows out of the defroster and foot vents, the control door doesn't operate, I believe i have lost the vacuum that controls that.


locate the vacuum leak by operating the non functioning doors and listening ... You will hear a suction sound...
Run the noise down and replace the vacuume line.

Sep 24, 2010 | Ford F-150 Cars & Trucks

1 Answer

2003 grand marquis a/c does not come out vents,only defrost and floor


the vacuum harness connected to the back of the control head is not fitting tightly any more. Pull narrow trim panel covering control head. remove 4 screws holding control head on.
Pull control head back. Fit 2 ten inch tie straps so they hold the vacuum harness (5 hose) tight to the control head. You can remove 2 torx bolts to lift bottom cover if necessary.
Vacuum harness is $20 F5VY-19C827-A, but I doubt you will need it.

Hold it tight with your hand to test before you do repair.

Gov't requires system to fail safe to defrost if a vacuum leak occurs.
I can post a photo of repair if necessary.

If that does not fix, Gino in California fixes internal control leaks.

Jul 07, 2010 | 2003 Mercury Grand Marquis

4 Answers

climate controls


Car manufacturers use the defrost mode as a default for safety reasons. Being they want you to be able to defrost the windshield no matter what. So when something goes wrong the system automatically goes to the defrost mode. You most likely don't have the vacuum hose connected under the dash at the climate control assy. Or if this vehicle doesn't use the vacuum hose style you may have not plugged in one of the connectors under the dash or behind the climate control assy. Good luck.

May 21, 2009 | 1997 Lincoln Continental

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