1997 Ford Aerostar presser relief valve?

I noticed oil leaking in between the clutch and compressor at the end of last summer. during the winter I noticed when the heat was on the ac clutch cycled rapidly presuming a leak possibly at the compressor, no pressure replaced both orfice tubes charge it, it outomatically leaks out what appears to be a pressure relief valve on the hose assembly that mounts to the back of the ac compressor.It does not get cold have to manually activate ac switch?Even though the compressor seems to work, could that be my problem, thanks