Completed cooling tune ups for both upstairs & downstairs, everything looked good to go on the upstairs unit. The downstairs had pressures/temperatures reading lower than normal. Couldn’t see any oil stains on the condenser but when I checked the evaporator coil it had a dark black spot on the edge of the coil. Took pictures & showed the customer & mentioned they don’t make coils for R-22 anymore & the only thing we could do is add refrigerant but it would eventually leak. She said she’d keep an eye on it to see if it struggles in the near future & go from there, no other issues to report.