The "HOLD" light comes on sometimes and blinks. Everything works fine. on 1992 Mazda Protege

Started months ago,(wife says) on for a while blinking, then out for weeks at a it's back on blinking. Everything works fine. A/C could be a little colder. Mechanic installed re-manufactured compressor, and changed to R-136A...just not cold enough..this is Clearwater,FL.