Fix vacum leak

SOURCE: 1999 Buick Regal temp problems

warm air come out on the passager side you got dual heating control the motor that control the hot and cold is stuck that hapen when the car sit there a long time or the setting dont move if it passager side under the dash you got the heater box about 3/4 down you got a square electric motor start the car gently tap the motor with anything you got most of the time it gonna start moving play with the heater control to see it move good luck pierre

SOURCE: dual heat and ac system

broken cable? if possible trace the cables back to the box move then bolth and see if one doesnt, if so you could alwase manually move it for a temp fix

SOURCE: air conditioner blower

I found the vac lin broke under the battery

SOURCE: I have a 99 Buick LeSabre with the same problem.

for my 1975 buick lesabre it was a vacume hose that conected to the fire wall i also learned that behind the clove box theier are two control arms one on top one on the bottom i believe the top controled hot and cold the bottom controled driver and pass ie left vents or right vents thank you ifixed mine hope the same 4 u

SOURCE: 1997 buick lesabre HEATER PROBLEMS The fan

This could be several things. First I would check that the thermostat is not stuck open. This will condition will make the car run cold when it is cold outside.

If this is not the case........and I'm assuming you've already checked that the antifreeze is full, make sure that the heater valve is working. If it is frozen in place then it won't move and won't allow the warm water to circulate through the heater core.

I'm basing my answers on a standard Lesabre. Yours may not have the standard climate control.