When I bought my vehicle from my buddy, the A/C only worked on "max A/C," and I was able to adjust the temperature of it. It would blow through the vents very forcefully, and it was ice-cold. As off recently, the A/C stopped blowing, but when I am driving cold air comes through the vents when I have it on "max A/C." It does not blow it just kind of comes through the vent but with no real force, when I am stopped there is no airflow at all. About a month ago I was driving off-road, causing my truck to shake around violently, and for the rest of my drive, it was blowing through my vents the same as when I bought my truck. After I turned my vehicle off, it went back to the way it was behaving previously (and now).

As a side note-- When I start up my truck and look under the hood, the A/C accumulator has condensation on it after it runs for about 30 seconds.

2007 3.0 liter

 

I don't know if this is the issue but I got really confused a little ago with my cars blower not sending air through the vents. I thought it was the blower resistor pack and changed it or the blower it self for like a week. Turns out the evaporator coil was just freezing up to a block of ice in my dash so air couldn't get through. Wasted a ton of time then just realized i had to let it thaw if it froze and keep fan speed on max when running ac. Might be your issue but idk.

 

Yes, frozen evaporator could be the reason

After AC has been running for say 15mins check under hood to see if ICE is forming on the Evaporators metal tubes, if so then AC is running TOO COLD and ice is forming inside the "air box" blocking air flow
Too cold is below 40deg, moisture/water in the air freezes at 32deg, and forms ice inside the air box on evaporator fins blocking air flow from the fan into the cab
Off-road vibrations may have been breaking ice free as it formed

Too cold usually means AC system is LOW on refrigerant and needs a recharge
AC works by Refrigerant at on High Pressure side(Compressed) being release to the Low Pressure side(evaporator), if the low pressure side gets TOO LOW then it cools down TOO MUCH, below freezing temps, and evaporator gets blocked with ice


And just a word on How it works
AC is on or off, there is no high or low, or any temp control, its ON or OFF
Difference between AC and MAX AC is a Vent setting, MAX AC closes the outside air Vent so all the air is pulled in from the cab(passenger side under glove box), so AC is re-cooling already cooled air instead of hotter outside air, which means cooler air after a few minutes
MAX AC also redirects coolant around the Heater core in the cab, it closes the By-pass valve on the heater hose in engine bay so heater core cools off, less heat in the cab

Temp control is done by the electric Blend Door in the cab, its a door that routes air from the fan either THRU the heater core(HOT) or around the heater core(COLD), or any where in between

The AC Compressor is on in all settings except OFF and VENT, this is done winter and summer to Dry the Air coming in to the cab, thats the water you see dripping from under all vehicles with AC, the more humid the outside air the more water drips out, or the more water FREEZES on the evaporator
The heater is way hotter than AC is cooler, coolant runs at 190deg, so any cooling effect in the winter with AC on to dry the air can't overcome the 190deg heat the heater core provides