Re: R12 to R134a a/c conversion
I had my ac converted about 4 months ago, it worked for while till it start to leak!! This conversion is somewhat simple, they have to "retrofit" the hi side (I think) to accept R134a. If your o-rings are in good condition and you might not get leak(s), but ask them to put some leak detector alone with R134a (it is going to be easier to detect any leak(s) in the future.
It should cost around $150 and all they did was evac your old R12 and putting some oil and new R134a. Keep you eyes on your sight glass and look for any bubbles after the conversion, bubbles usually indicated leak in the system (fact, late model ac units are closed units).