My SL2 has 174K miles on it;I notice a ticking or rattling noise when I engage

When the a/c is turned on the compressor switches on, runs until the selected coolness of temperature is achieved and then it switches off. Compressor may be bad, compressor clutch may be going bad or refrigerant may be low. It's hard to say if the noise is abnormal without hearing it and being able to do basic diagnostic tests.