91 Lesabre air conditioning problem

I have a 91 Lesabre limited that has a full charge and produces cold air when turned on. However after driving about 10 miles, the blower still blows, but the cooling is lost. Can you Help?

I would rap on the compressor control relay on the firewall when a/c is inop, that is most likely the problem. However it could also be the pressure cycling swith located on the accumulator. You should rap test it as well.