1999 buick park avenue cold air on left hot air on right side of car I can't find the actuator air mix rod to try that I have removed the glove box and don't see it

There are 2possibles ,1. The heat / cool slide control is defective, it is not possible to repair. Most likely the servo motor that opens and closes the air vent that gives you heat or cool is stuck. Open your glove box and you will see 2 rubber tabs that hold the door at the open and down position. Push down on your glove box door until it swings all the way down (this wil be past normal open) up inside you will see a metal rod affixed to a arm that pivots via the servo left is full vent(cool) right is full heat. Push your hot/cold heat selector and see if it moves. It may not be moving its full extension. If your not sure push it right and you should get heat push it left and you should get cool check YouTube this is a common problem for this era of Buicks, good luck Bret

This is best left to a professional.

There is a problem with the drivers side air mix valve. I have seen several problems with these. Sometimes the air mix valve (door) gets stuck and when you try to change it the air mix valve link can pop loose, or sometimes it breaks. Sometimes it also breaks the bellcrank on the door itself. The programmer unit can also be defective. Please refer to the picture below. The thing to do is to remove the lower hush panel and possibly the glove box assembly so you can get a good look at what is going on. Then switch the driver's temperature control from hot to cold and back again to observe the movement of the programmer actuator, the mix valve link, etc. to determine where the malfunction is.

The vacuum motor may be bad:

Vacuum Actuators Fig. 1: Vacuum actuators and related parts
REMOVAL & INSTALLATION

1. Refer to the Air Bag section at the beginning of this Section, and disarm the Air Bag system. Disconnect the negative battery cable.
2. Remove the glove box assembly.
3. Remove the right and left side sound insulators.
4. Remove the heater ductwork.
5. Disconnect the hose harness from the actuator.
6. Disconnect the actuator rod or lever.
7. Remove the mode, recirc, or A/C-defrost actuator. To install:
   
8. Install the actuator.
9. Connect the actuator rod or lever.
10. Connect the hose harness to the actuator and fully seat.
11. Install the heater ductwork.
12. Install the right and left side sound insulators.
13. Install the glove box assembly.
14. Refer to the Air Bag section at the beginning of this Section, and arm the Air Bag system.

open the glove box and make it fall down.behind the glove box there are two melel rods one on top one on the bottom. move the top one to the passager side, everytime you shut the car off you have to do this

The actuator motor is bad and needs to be replaced for the right side.

U need to replace the air temperature control blend door actuator motor, this requires removing the dash to access the motor for the blend door.

Behind the glove box you will see the heater box. On top of the heater box you will see a set of wires going to a small controller box that has an arm on it. It is probably not working and you can only by them at the dealer. It is the dual climate controller and cost approx. $100.

sounds like the drivers temp door actuator is not working should be located on the drivers side of the air box down by the gas pedal or center dash area

Three possible issues. First... which side seems to respond to to the control input? That will tell. There is an actuator behind the glove box slightly above it. You can see it as it is attached with the metal rod. Simply open the box and pull it down. There are two rubber keepers that flex and allow it to open completely. When you id the part...simply try to move it (the rod) and the actuator by hand. A good actuator cannot be moved by hand. You can also start the car and select between hot and cold and it should move as well as the one just below it.( just about even with the bottom of the glove box. Let me know and I can give you a little more info later...