Hi Bob,
I also have a 2001 ZX2 and my AC operation is intermittent with the compressor clutch sometimes working, sometimes not. I have since searched the 'net and have also obtained a set of Ford wiring diagrams for this car. The problem seems to lie in a device Ford calls a 'Constant Control Relay Module' or CCRM for short. It is located in the engine compartment under the air filter housing. From what I can gather from various places on the 'net the failure of the CCRM and hence the intermittent/non operation of the AC is VERY COMMON on 1999+ Ford Escorts and ZX2s (and other Fords). A small relay inside the CCRM (of which there are many) fails. A new CCRM from Ford will set you back over $200. There are other workarounds that have been used. Email me if you want more technical info.
Paul
paul78zephyr@verizon.net
Paul
September 2005