2002 Venture - A/C shuts down

The A/C in my venture is not working properly. When I put it on high (No 5) on the knob, it blows cold air and then after a few minutes it shuts down. I have to turn it off and turn it back on again to get it started again, only to shut down again after a few minutes. It only does this on the max (No. 5) setting.

What can this be?

Low on R134A ? Read the pressures.