Compressor

Hi. If the compressor is working properly you should be able to feel a throbbing from the machine, and if you remove the inlet filter there should be condensation or ice on the cold pipes.

If it is throbbing but not producing cold pipes, then the refrigerant may have been lost through a leak. Not a DIY job I'm afraid.

If these suggestions do help you solve the problem, please give my reply a rating to help others judge my knowledge / guessing skills.
If they do not, please hold off on the rating and add a comment with more details so I can try to help you further. Cheers, D