Question about Buick Century

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03 buick century, ac control knob blows out on all vents regardless where I position it. David

I can put on heat, ac, defrost, bi-level, air blows out on top, middle and bottom vents. Thanks David

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  • 434 Answers

This usually is related to the vacuum reservior tank/cannister or the hose leading to that chamber. Any other vacuum hose leak could cause a similar problem depending upon it's location.

The hose leading to the cannister is usually just a thin single hose/tube leading to the cannister. The system allows vacuum to build up in the vehicle and maintains vacuum on the A/C system under heavy acceleration where a loss of vacuum would cause the A/C to change operation (switching from defrost to other venting and vice-versa) due to the loss.

You could have a cracked vacuum hose, or a cracked cannister.

You can use regular carburetor cleaner in a spray can with a nozzle, and carefully spray the vacuum lines on your vehicle when idling, and should notice a change in RPMs if you spray near a leak. Only spray a small amount at a time and let the engine compartment air out between spraying/testing since this is a flammable product.

This should lead you to identify any leaks.

Good luck!

Posted on Mar 29, 2012

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Posted on Jan 02, 2017

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Tim Whalen

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SOURCE: 1999 buick lesabre air works

I would check under the dash to see if a hose has come disconnected for the middle vents

Posted on Aug 08, 2010

Anonymous

  • 146 Answers

SOURCE: 1998 Mustang - AC blows only through Defrost vents

You probably have a vacuum leak on the passenger side. its a small plastic hose some times they come unpluged from the engine. or brake.

Posted on Jan 05, 2009

mikehumble

  • 124 Answers

SOURCE: heater control 98 chevy s10 blazer

These trucks have a problem where moisture builds up in the heater box then freezes. When this freezes and you change your heater settings it breaks the shaft for the blend door. If this is what happened you should be able to look under the dash above and to the right of the gas pedal and you will see two vaccuum accuators one of them you should be able to wiggle around the linkage if it is broke. To fix this you need to remove the entire dash to get the heater box out which involves discharging the AC and draining the coolant because the heater core and evaporator come out. Please rate.

Posted on Dec 13, 2008

Anonymous

  • 1 Answer

SOURCE: ac only blows through defrost vents

I just found my problem that often brings in a Check Engine light, and reads out a PO 442 code. When my A/C is on my heater would start working because a vacuum operated control door would slam shut when accelerating. Also my cruise control would stop when going up a large incline.

the first thing to check, and easy is the cruise control for a bladder leak. Look on the top side passenger side of the firewall, and you will find a three way vacuum hose connection. One will be a very small black plastic line that runs to the cruise vacuum actuator. Pull this hose loose at the fire wall connection. Blow in this hose, and if it will not hold pressure, and in my case I could hear air passing through it is defective needing replacement. Block off the firewall connection for A temporary fix.

Posted on May 08, 2009

Ted Schore

  • 7353 Answers

SOURCE: Air only blows outthe defroster vents on top of the dash

unhook battery, rehook battery, turn key on, ..............wait 2 minutes, then start truck and ck a/c. sometimes it works, if not, it will need to be checked by a shop .

Posted on Sep 24, 2009

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