Well I don't know what the hell is happening now

Drove home from work and selected "Lo" using the "Auto" function (climate control), which activates the aircon and air recycle. After a few miles she started blowing cold air, not just "off warm" but actualy cold

Turned the a/c off for a mile or so and the air became warm. Back on with the a/c and she starts to get cold again!! Not the ice cold that I've had in the distant past, but refreshingly minty

I wonder if there's a blockage somewhere.
I need an aircon expert to check this out... hmmm...