Added new freon to system. Air clutch engaged and working properly. Get ice cold air for a short while and then goes hot. Will do this back and forth. Any ideas on what could be wrong.

 

It might be that the thermostatic control that should turn off the compressor when the cold chamber is cold enough is not working. This results in the matrix icing up and no cold air. Or, conversely, it could be that the thermostat is turning off the compressor too early resulting in the same problem. How to fix it, I have no idea, I am sorry to say. But it is worth seeing what is happening to the compressor engagement when the cold stops happening.
You car is at about the change-over date for the aircon system. Do you have the Delanair 3 unit or the D 2? The D 3 has a pull out feature on the temp selector (LHS) knob that gives full cold and over-rides everything else. If you do have the D3, what happens when you do pull the knob out? If doing that does produce cold air properly, post again as there is a fix for that.

 

He has a Mk3 Delanair system. They came in 1987 model year.
Jon

 

Can you post your low and high side pressure readings? Without that all we can do is guess.