I've had a couple cases where I took apart and cleaned the
outdoor unit, and the AC came back to life. Please make a few
calls, and see if you can find a HVAC service company that's
willing to take apart and clean the outdoor unit. They should use
chemicals (sprayed on) and then a water hose to rinse it clean.

I'm not there to get all the readings, but it sounds like your
unit can run for several more years.

I ended up calling a repairman. He located a leak in the evaporator
tubing inside the air handler located in the attic. He recommended
either replacing the entire Carrier air handler ($1600 - 1800) or the
entire system for with Lennox 14ACX / CBX26UH system for about $3300.

While getting quotes, some said you might as well switch to the R410A
refrigerant as R22 will be start to phase out in 2009. Others said R22
is cheaper and will be around for a long while. Is it better to stick
with a 14 SEER R22 system?