a/c pump 92 sunbird

I own a 92 sunbird le and when I run the a/c or defrost my a/c pumps makes a very loud grinding noise and the a/c is blowing cold air. I was told usually they just seize and it's done. Does this mean I have to replace the pump just to get my defrost to work because I can live without the a/c. PS the noise is not made if I have the heat on.

The A/C doesn't kick on in defrost mode when the temp is too cold outside. You can just unplug the a/c clutch and your a/c won't kick on at all until you plug it back in.