06' buick la crosse only blows cold air when it is set to 90*

Put heat on max, only get cold air

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.

the climate control thermostat is not opening the valve to let the warm coolant in

Assuming that none of the Electrical/Electronic controls were disturbed when changing the Thermostat it seems to me that you have an "Air Lock" within the heater. One must purge all the air out of the cooling system as close to the highest point as possible after the system has been partially or fully drained. Most of the time one will find small BRASS Bleeder Valves located somewhere near the highest point. Open each one while the system is pressurized and let Air escape until some Coolant escapes. Sometimes it may be necessary to loosen a Heater Hose and bleed the air at that point. Remember that the system MUST BE PRESSURIZED to accomplish the Bleeding of Air. Many auto parts stores sell hand pumps with a pressure gauge for this purpose and leak testing. These pumps typically replace the Radiator Pressure Cap temporarily. The system does not have to be at normal operating temperature to bleed the air out. Once the Air has been bled you will have to refill the radiator to normal full and make sure that the Coolant Recovery Tank level is also brought up to recommended level. A quick check is to remove the Radiator Pressure Cap, Start the Engine, Rev the engine suddenly (A short Jab) and see if the coolant level falls rapidly in the radiator. If it does it is definitely an AIR LOCK situation.

Fastest Robe

the motor for the passenger side
blend door is shot

I had the same problem when i was working on my 1999 Buick Regal and had to disconnect the battery. I didn't reconnect in the same way that I disconnected the battery from the terminal and noticed that the driver side had no heat or air but the passenger side did. I then disconnected the battery again and reconnected it the same way and now have heat and air on both the driver and passenger side. Hope this helps. Good Luck!