On my 92, I left all the factory ac wiring in place. It isn't tied to the new ECM at all. I run one of my cooling fans off the pressure switch and a relay, so the fan comes on when the compressor engages. The only thing you can't do with this setup is alter idle in the ac idle table as you have no signal to the ECM. My truck idles fine when the ac kicks on though. I'm using the original compressor on a dirty dingo bracket.
1992 rcsb 5.3 lm7, NV3500
2012 corvette vert, ls3
Both tuned by me with HP Tuners