2001 Aurora A/C compressor won't kick in

I have a 2001 aurora. the A/C compressor won't kick in. could this be as simple as a relay or are there other reasons?

Can someone tell me which relay takes care of turning the compressor on? I'm hoping this could be something simple but there are a few relays in the box.

Your two posts have been merged together since they are the same issue.

Look for the relay that says A/C Clutch and there should be a clutch diode. The PCM module (computer) energizes the relay providing there are no issues like a HVAC DTC(s) or a low or excessively high refrigerant charge.