1997 Chevy S10 4.3 Vortex New complete ac system not working

I have a 97 chevy s10 4.3. Did a complete new ac system installation. Install new ac pump and put oil in holes, new condensor, new accumulator, new evap core, orifice tube, ac hoses. Did a vacuum for a couple of min it went to -28 closed the manifold gauges and turned off vacuum pump..waiting 30mins it held -28. Next added freon and put about 3 cans of freon. System took freon starting cooling fine. Ran truck for about two hours then heard some noises near glove box then ac started losing its cool slowly. Did i over charge? not enough oil in compressor? Did i damage compressor? How can i check compressor before i buy another..

Number one cause of mobile A/C failure is loss of refrigerant due to a leak. What is pressure of system as it sits with engine off? If less than 47 psi, the evaporator freeze protection switch will not allow compressor to come on, you can test by jumpering the connector to the switch on the accumulator. But chances are real good you lost most of your refrigerant - especially since you said it gradually stopped cooling. Look for oily residue about any and all refrigerant line connections- there are times when systems will hold vacuum, but leak under pressure and vice versa.....so a pressure check is in order first.