possible evaporator leak

Gentlemen:A few years back I did a conversion from r12 to r134a. I checked for a leak with dye and could find no dye. I ask the whats the probability of a defected evaporator compared to a leaking ac fitting..

evaporaters are very fragile sometimes they crack so that could be a possibility also the fittings should be fine as long as you didnt cross strip them and made sure to replace any bad o-rings that looked like they were compressed

If you got a sniffer and still have some refrigerant in it, turn on the A/c while running with fan and sniff in the dash vent should tell you if it's leaking.