On several occasions I noticed white vapor blowing out of the two vents above the radio. Now, I noticed that one of these two vents is blowing cold air while the one next to it is blowing warmer air. Any thoughts?

 

Check the pressures of your AC refrigerant (low & high sides).

It might just be normal, especially if it's extra humid outside.

The cold AC evaporator removes moisture from the air, like a dehumidifier. But to make the heater/AC package ever more compact, sometimes some of the water vapor gets through. That's not unusual.

But if the refrigerant pressure is too low, the temperature gets colder, but the "cooling power" is less so it doesn't cool the entire surface of the evaporator. Then it can get different temperatures in different parts of the AC.

But have the pressures measured. If you just go & add R134a you risk damage in case the problem goes beyond simple low-pressure. Besides, if the pressure is low, you'll want to find the leak & fix it.

 

Finally got the AC checked out. There was no refrigerant at all in the system. I had the mechanic re-fill it and they also added some flourescent dye to try and detect the source of the leak.

It's been almost one month now and no leaks have been detected. I suspect once the weather warms up the leak will reveal itself....?