Air does not flow from the vents on my 1997

The 2 vents on the drivers side have warm air blowing out. ... But a system that is 1/2 pound low will cause the passenger side vents to blow cool or cold air, and the drivers side to be less cool or even warm on this car. There is simply not enough freon capacity in the system to cool the air to the drivers side.
https://www.justautorepair.com/buick/century/cool-passenger-warm-driver

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Cornelius, vent problem could be a pinched or loose vacuum line on controller,faulty AC vacuum motor, faulty AC programmer,etc. needs to be checked out by a good Tech, diagnosed and estimate on repair.
As far as vehicle only blowing cool air, issue could be blend door issue, plugged AC condenser core dirt/debris, low AC refrigerant, plugged AC lines internal, failing compressor, etc., again should be checked out, diagnosed and estimate for repair by a good Tech.
Check the attached links,instruction and guides, Good luck
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1998 Buick Lesabre No Air From Dash Vents
http://repairpal.com/ac-vent-problem-346
Car AC Not Blowing Cold Enough Car Repair Information From MasterTechMark
My Car Is Not Cold What Could be Wrong Elite Auto Repair

Sounds like a blend door problem under the dash.

Under the dash you have the vacuum motors or servos or
electric door motors, for the hvac switching of air flow

So a vacuum leak or bad motor, whichever you have or binding
doors,also there may be linkage to some of them that gets into
trouble.

Hard to work or see things under the dash

If you have any electronics with an auto heat & a/c system then you
will need manuals to diagnose

You have a vacuum problem either to the AC control head or a problem with the ac control head.

common problem, check under dash by the gas pedal if control arms are muving went selecting from ac to heat cuz this it is the control for the vents to go from ac to heat and to defrost.

I found the vac lin broke under the battery

heater blowing cold when engine idleing,works good when rpm are up. what is problem? pete