Ac BLOWING HOT AIR INSTEAD OF COLD. All of a sudden my AC started blowing hot air instead of cold. It is set on cool.

There are a lot or reasons. Here is a post. https://gobdp.com/blog/car-ac-blowing-hot-air

you probably need to recharge the system go to you local auto parts store and ask them for help they will show you how to do it. LARRY B

Sounds like a bad or stuck reversing valve. Typically r.vs. are energized in cooling, verify 24 volts to valve, if yes , bad valve

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possibly low coolant, that will make the clutch disengaged and you get hot air instead,

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The thermostat controls the discharge temperature by using the compressor to cool and mixing hot water from the engine to match the setting. When you select AC, it enables the compressor to run from the thermostat. Else, only outdoor air is available.

2004 chevy Avalanches air conditioner blows hot air, can the actuator be forced to keep it blowing cold air instead of hot air all the time.

I would check the following possibilities:
1. Is compressor clutch working? - You need to do this when the ac is blowing hot air only - locate compressor drive pulley on engine - rubber belt wraps around it. Start engine and set to max ac. When the ac is blowing hot air, look at the center of the compressor drive pulley using a good flash light - watch it for a while, it should be spinning with the pulley - this means the compressor is engaged. If not, the compressor is not engaged. If your ac is blowing hot air, then the compressor should be engaged and running (trying to cool). If it is not engaged, then your compressor clutch is probably going out. Could be low voltage to clutch, but more likely the clutch is worn out and only working some of the time. Note: if working normally, the compressor clutch will engage and disengage in cycles- but the air should always be cold. If clutch is bad, compressor would need to be replaced (sold as one unit). This is tricky to diagnose and could take some time - you need to do it when ac is blowing hot air but set to max cooling.

2. Low on refrigerant or refrigerant has moisture in it? If your ac blows cold initially after being off for a while, then heats up, and continues to regularly cycle back and forth between hot and cool air, then the system may be low on refrigerant or the refrigerant may have moisture in it that is freezing and restricting refrigerant flow. An a/c shop can check refrigerant level and even replace refrigerant if moisture is suspected.

Could be other issues, but I would start with these.

Good luck

the blend motor on the vehicle is probably bad

Your A/C sounds like it needs to be vacuumed
out and then recharged to factory specs. That
should solve the problem.

Check for the following problems
(1) Check if compressor is geting power
(2) Check if system have Refrigerant in it
(3) Check if pressure switches are operational
(4) Check Thermostrat setting.
(5) Check for dirty or block condenser or evaporator

Send feed back if you solve problem