XJ6 & XJ12 Series I, II & III 1968-1992

ac blows out defrost vents

 
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Old 05-24-2014, 11:02 AM
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Default ac blows out defrost vents

1987 series 3 xj6-I can hear and see the servo adjusting eith the temp dial but the ac seems to blow cold air from the defrost vent primarily with little to none on the faicia and lower vent. it there a way to adjust this to get it to close the defrost flaps?
Thanks
Jeff
 
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Old 05-24-2014, 11:29 AM
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check a little plastic check valve located next to the battery sort of hanging from a vacuum hose which goes through the firewall to the a/c system;

First note the orientation of the check valve before removing the vacuum hoses, then remove the check valve and blow through it one way and then the other end, one way should allow air through, the other way should not.

if air comes out when blowing on either side, the check valve is stuck or clogged, try putting it in a pan with warm water for around 20 minutes to see if it gets unstuck, then try blowing again.
 
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Old 05-24-2014, 12:54 PM
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Originally Posted by wardhill View Post
1987 series 3 xj6-I can hear and see the servo adjusting eith the temp dial but the ac seems to blow cold air from the defrost vent primarily with little to none on the faicia and lower vent. it there a way to adjust this to get it to close the defrost flaps?
Thanks
Jeff

Jose is starting you off on the right track as the sytem depends on vacuum supply to operate the various flaps that direct the air. After checking the valve look for stray vacuum hoses and make sure the vacuum reservoir hose is attached as well.

When full cooling is called for the center vent should open and the defroster flaps should close, obviously. This is accomplished by a couple different vacuum switches and checking them gets a little involved....so make sure the vacuum supply is good first.

What happens when you ask for heat? Does the ariflow start coming out of the footwell vents? if so, this suggests that your vacuum *supply* is OK but the vacuum switching is on the blink.

You mentioned 'adjustment'. Yes, the system has some adjustments ....pertaining to the mechanical linkages coming off the servo assembly....BUT unless things have been taken apart they shouldn't need readjusting. I wouldn't 'go there' at this point!

Cheers
DD
 
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Old 05-25-2014, 11:34 PM
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Thanks,
I've been away for graduations . I'll check the valve and hoses tomorrow. When I switch to heat mode I also hear the servo but it still predominately blows from the defroster vents with a little at the floor and some at the rear center
Regards,
Jeff
 
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Old 05-26-2014, 03:42 PM
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I pulled the check valve and can blow air through in one direction but not the other . Does this indicate the valve is stuck open and need attention?
 
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Old 05-26-2014, 04:41 PM
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no, it means the little valve is good. Make sure you reinstall it in the same orientation it was.

next check would be to visually check the vent flap linkages located on the passenger side, front of center console. Remove the side vent panel by unscrewing the two phillips screws on the black plastic vent grille, remove grille, pull finishing panel towards front of car, then you can see all the linkages.

with engine running, turn a/c ON and watch the linkages move up, sideways, and down to see if any of the adjusting detente/stop nuts are loose. But don't touch anything, like Doug said, "don't go there". If you see a lose link, first look for any marks where the STOP NUT may have scratched the link, that may be where it was originally.
 
Attached Thumbnails ac blows out defrost vents-vent-flap-linkages.jpg  

Last edited by Jose; 05-26-2014 at 04:54 PM.
 
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