A/C not working, just blowing hot air.

Make sure your blend door is closing all the way and that the actuator actually works.

I would make sure the shut off valve between the cold air and warm air is engaging. this is controlled by a vacume

see this steps and think with clearly and logically NOT feared. God bless you
Start with the compressor. Does it engage when you turn on the A/C?
If so, the compressor is working and the A/C system probably contains enough refrigerant to make cold air, so the problem is inside the HVAC unit. Replace the motor that controls the blend air door (this is a difficult job and best left to a professional since it involves tearing apart the HVAC unit -- about an 8 to 10 hour job!).
If the compressor does not engage when you turn on the A/C, see if it will run by jumping the compressor clutch wire directly to the battery (use a fused jumper wire). If the compressor works when you jump it, and the A/C blows cold air, the system contains refrigerant and the fault is likely a bad A/C compressor clutch relay or a bad clutch cycling switch or pressure switch.
If the compressor does not engage when you jump it, the problem is a bad compressor clutch.
If the clutch engages but the compressor does not turn (the belt will start to slip and squeal), the compressor is locked up and you need a new compressor.
If the compressor clutch engages and turns the compressor, but the A/C still does not blow cold air, the system is probably low on refrigerant and needs to be recharged.

The question is: why isn't the compressor clutch turning

The compressor isn't likely seized,it may leak refrigerant,
but won't be what your asking.

The clutch can be jumped to test that

If okey, then you have to diagnose the entire
A/C Electrical System

How do you know it is properly charged,you put
refrigerant gauges on the system?

There are a number of possibilities.
1. If the compressor has a clutch, do you hear it engaging and disengaging?
2. The valve controlling the hot water going to the heater which mixes warm air with the cold air from the evaporator, is not working properly so it si not maintaining proper temperature.
3. THe temperature sensor that senses air temp at the intake to the AC in the cabin is defective.
4. THis is too comlicated to fix yourself, so you need to take it to an AC expert who knows this particular model.

I have 2000 ES300

The only other thing then would be if the compressor is turning, engaging, and the cooling fan working properly. You should either be able to see the compressor clutch engage, as the switch is energized, or at least hear it click loudly when the switch is energized. If it is not, then there are sensors for the low pressure/high pressure line to tell the compressor when to function, that also have to be checked.

As the engine runs with the compressor turning, one line should be hot/warm, the othe,r (larger diameter hose) should be cool/cold, if the system is working properly.

If the compressor is turning when you have the A/C turned on, then see if the cooling fan is running as well. It must run to remove the heat and cause the process to function properly.

Good luck!

it may be that the clutch on the A/C compressor is faulty & sometimes it doesn't engage or it could be a wire is loose or a loose connector plug, next time it blows hot air when it should be cold lift the hood & make sure that the clutch on the A/C is engaged ......hope this helps......cheers.

That could be a variety of problems. The first thing you might do is this. When it isn't working, open the hood and see if the clutch on the A/C compressor is cycling. If it engages and disengages while the air conditioning is on, that would indicate that the problem might be ducting or another issue. If the clutch doesn't cycle, one of the first things I would check would be to see if there was power to the clutch when the A/C is turned on. It would be helpful to know what your vehicle is, such as year, model, and if it's equipped with Automatic Climate Control like many Buicks are.

Air Conditioner blows warm air

1. Air conditioner system is discharged. Have the system evacuated, charged and leak tested by an MVAC certified technician, utilizing approved recovery/recycling equipment. Repair as necessary.
2. Air conditioner compressor clutch not engaging. Check compressor clutch wiring, electrical connections and compressor clutch, and repair or replace as necessary.

the air blend door inside the heating / cooling unit that sits under the dash is probably not moving. there is an electric motor and control unit that moves the air blend door (assuming you have the electric dial or push button digital controls. some of these vehicles have a valve that shuts off the antifreeze from cycling through the heater and if it remains open then you would get "not hot" but just warm air.