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Registered
1997 Deville Basic
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5 Posts
Discussion Starter #1
After a week of searching past discussions on this subject I repaired the cause of the problem. The
vac line to the canister was broken and now I have full vacuum to the HVAC hose to the interior. Isn't
there a way to re-set the AC system so that it will start blowing out the dash? The problem started
when I had left side vents blowing hot air and right side blowing cold air but they were all blowing out the dash. I manually moved the blend door to get cold air but for some reason it moved it to defrost.
It will change from hot to cold as it should but only blows out defrost.

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This is a 1997 Deville base model
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
Joined
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19,250 Posts
After a week of searching past discussions on this subject I repaired the cause of the problem. The
vac line to the canister was broken and now I have full vacuum to the HVAC hose to the interior. Isn't
there a way to re-set the AC system so that it will start blowing out the dash? The problem started
when I had left side vents blowing hot air and right side blowing cold air but they were all blowing out the dash. I manually moved the blend door to get cold air but for some reason it moved it to defrost.
It will change from hot to cold as it should but only blows out defrost.

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This is a 1997 Deville base model
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your system MODE is vacuum controlled -
DEFROST id the "default" position -

the most common problem is a vacuum leak -

the auto parking brake release is on the same vacuum circuit -

if it doesn't work -
the most common cause is a leaking diaphragm in the parking brake release -

start checking for vacuum leaks -
 

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Registered
1997 Deville Basic
Joined
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5 Posts
Discussion Starter #3
I plugged the parking brake line. It has strong vacuum but no change. Is there a way to manually change it to dash?
 

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Registered
98 DeVille, 97 DeVille d'Elegance
Joined
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7,345 Posts
The actuator is center under dash. There are 2 there, one does 2 actions the other does one, i would have to check fsmfor operations. The main vac source is under pass dash and is controlled by small electric selenoids. I had issues with filter disintegrate and plugging the valves (still occurs occasionally so I think the selenoids are weak or main hvac controller is going out). The wife is none too happy as it is 100 degrees and has been happening often this week.
 
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