I'm having problems with my 92 Buick PA air conditioning system.

I've replaced the compressor, recharged the system with no leaks,
replaced the ATC vacuum system behind the dash, checked the low
pressure sensor, and replaced a relay under the hood. I've reset the
codes which show long term freon loss but it still doesn't work.  If I
unhook the battery it will work for a few cycles and then revert to the
same code.  I'm guessing something electrical but what and how to
do d it