AC blows hot
 

My AC is blowing hot. The compressor works and is engaged, my gauge says it's full of freon(normal levels), my condenser an lines are cold and sweating. I'm not losing any coolant. When I got the car the compressor never kicked on but I pushed a little freon into the low pressure port and it kicked right on. I used the whole can and the pressure only moved from about 26psi to about 28 psi. It's holding pressure. What could this be? Maybe the blend door spring?

Could just be low, one can could have been enough to kick on the low pressure switch but the system is still low. You will need to look at the high side pressure to be sure. High side pressure does vary a lot because of environment so if you have a working car you could verify high side on that car.

Where is the high side port? And can I check it with the same gauge or are they different sizes?

Its a different size. I use the manifold gages for AC, I am not sure what else you can use.

Low side is the suction side with the larger diameter hose/line. The smaller line is the high side. High side runs from the compressor to the condenser then to the evaporator. Port can be anywhere a long that path.