I have been having problems with my AC and am getting "low refrig A/C off"

THE "LOW REFG / AC OFF" CODE WILL NOT LET THE COMPRESSOR START. THEREFORE YOU CANNOT ADD ANY REFG TO THE LOW SIDE. I HAD THE SAME PROB. MY MECH GURU CLEARED THE CODE AND ALL IS WELL NOW. ( SLIGHT LEAK AT THE COMPRESSOR ) WAY TO $$ TO REPLACE. NOW I JUST ADD A BIT OF FREON TWICE A YEAR BEFORE I GET THE CODE ..