2003 Corolla A/C problems

I have 140,000 miles on my Toyota Corolla Great Ride, but just started to have problems with AC.
I recharged system last weekend but still have same problem. TI turn on AC and sometimes it will work you can see compresser clutc engage and then stop and after awhile will start spinning again heater works fine and you can feel AC blows out when it does work it is not as cold as it should be Fuse is fine.
Is this a relay switch problem or a sensor?(Spelled wrong)Please help it is heating up