Home HVAC question.

[rscurtis]

The York central air system in my house has developed a leak in the evaporator of about 1# of R22 per month. The unit works fine (when fully charged), and is 19 years old. I don't know the model of the air handler. Here is the question- Is it typical to replace the entire air handler, or would a replacement evaporator core be available?. I know a whole new unit may be more efficient, but even at worst, my electric bills to not exceed $100/month, even last month. The compressor/condenser are the same age and are working fine, no leaks there.