A/C clutch after warm-up does not engage.

I would go to Getwrench.com and schedule a free diagnostic. We will send a mechanic to you and help you fix the problem.

Given your description of symptoms , two choices , bad relay , or worn/weak 'field coil(magnet) and clutch assembly. If it's the relay -about $20.00 part plus labor(1/2 hour for that diag , not to difficult) IF it is the field coil and clutch getting weak , replace the whole compressor as a unit , don't just do the clutch/coil.