A/C mysterey. Please help

A/C does not work.

Current diagnostic status:

All HVAC fuses are good.

Pressure is good and holding. ( had a friend use a reclaim machine to verify this )

Bypassing the A/C relay ( connecting the appropriate pins ) clicks the Compressor clutch. If engine is running, cold air comes through the vents, so the system works if forced into service.

Arcing the pins on the Low-Pressure cut off causes the electric fan to come on and the engine RPM to rise, but no compressor clutch. According to Haynes manual, doing this should kick the compressor on.

Swapping out the A/C relay doesn't change anything.

I've checked for loose or broken grounds under the chassis and in the engine bay, nothing. I've pulled the A/C switch out of the dash to look for similar issues, but nothing.

Any suggestions??

BTW: I have not been able to bypass the compressor cycling switch, which is located inside the evaporator core under the dash. Also, I have not hooked up my scanner to get the A/C on/off status info, but I suspect there will be little help there.

Thanks,

-Kevin