Over the last 2 or 3 summers I've had to have the HVAC tech come out once
the temp starts to climb, to re-charge the upstairs a/c with Freon (Trane
XE1000, 10 yr old unit). Obviously a leak, but cheaper to re-charge than to
fix. Since last summer the Freon charge didn't last the season, I've bit the
bullet and decided to repair the leak.

Tech came out and said the evaporator coil was corroded and was causing the
leak. The slow degradation of cooling power (versus sudden loss) was
indicatory of a bad evaporator coil, plus he visually observed corrosion.

Cost (parts, labor, installation) was $825. This seems high but wanted to
check to see if in fact it is.

Also, was told two things can cause corrosion of coil:

1) Running a/c at low outside temperatures. I don't do this but am the
second owner of the home so don't know what the previous owner did.

2) Dirty filters. I change them pretty regularly, every 45 to 60 days.
Again, don't know what first owner of the home did.

Will running the fan constantly help in case any ice does form on the
evaporator coil? I usually run the fan 24/7 to help distribute the air more
evenly.