I finally got my A/C back on my 72. I had Classic Auto Air flush the evaperator, clean and restore the POA, new expansion valve, new lines, drier, compressor and condenser.

I added 4 cans of R12 after a long evacuation. The A/C get cool, not cold. 80 degees ambient, low pressure 34 high pressure 220 outlet temp 60 degrees at 1500 -2000 RPMs There are no bubbles in the site glass, plenty of condensation dripping out of the box (all the way out the garage door) not freezing up. I put a box fan blowing in the condensor no effect.

Any idea what may be wrong?

The only thing I do know is a problem is the new compressor clutch slips with A/C off (wire unplugged from compressor). Is there any quick adjustment to stop this?

Is it possible that the AC/heater vacuum operated doors aren't operating correctly?

The doors open and close all the way but I will double check them tomorrow.

The hot/cold blend door is working properly, does anyone have any other ideas?

Doesn't the 72 have a shutoff valve in the heater hose? I believe it should.
If so. make sure it's actually closing off the coolant flow.

Those numbers look just about right and the condensation pouring out of the evap drain is an indication that it's cooling well. I suspect you have some reheating going on or a lot of your airflow is bypassing the evaporator for some reason.

-At 80*. your high side is a tad high, but not bad. Mist water from a garden hose over the condenser. How quickly does the pressure drop? Does the outlet temp drop?
-You said "4 cans of R12". What size cans, how many ounces per can?
-If you have access to some type of contact thermometer, measure the temp of the lines right where they go into the evaporator case and post it.

The 72's do not have a hot water valve but that is a good idea, I am going to crimp a heaterhose to block the flow to see if that helps. I can hear and feel the hot/cold door close and open when I move the lever. I used 12 oz cans.

I don't have a contact thermometer. I fixed my clutch air gap problem today so the compressor disengages now without dragging, I replaced the plate because the one that was on it was warped, beleive it or not it was new. Due to time I did not get to do a lot of diag work on it today.

Thanks for your help and keep the suggestions coning.

I was talking with James Hinshaw today and I mentioned my A/C problem to him and he had a suggestion.

72 was the first year they did not use hot water valves on the Chevelles. He said he had the same problem with his A/C in his 72, cooling down to 60 and not getting cold. He said the hot and cold air are fighting each other because the blend door is shut but hot air is still getting around it. He put a manual cutoff vavle on his 5/8 line and it cured his problem, his air gets cold. In order to make it look factory but not correct you would have to change the vacuum setup on the control head and run a vacuum line.

I am still going to clamp off the hose to test it and if it works I will add a small cut off valve in the heater hose. Here in the South the heat won't get turned on again until fall. The only downside is I won't be able to "warm" the A/C up on a mild morning.