We just purchased a two story home with a full basement. The AC is a 2.5ton Carrier system with Puron installed in 1999(The natural gas furnace is also carrier, but I am unsure how old it is..possibly 15 yrs old). This past week we had consistant days in the 90's and noticed some problems.
First off, we could not keep the house below 78. The upstairs was consistantly above 80 degrees. I have checked the attic insulation, and for our area (Twin Cities MN) it is atiquately insulated. The ducts on the second level have hardly any airflow coming through them whatsoever.
We have tried several things. First we closed the ducts on the main level of the home. This did nothing. Then we closed the basement door as we were told all our cold air was going to the basement. (our outside unit froze up once and we had to leave it off for quite some time.)
Then we have been trying a combination of the above. The outside unit hasn't frozen up since, but we are still having problems cooling.

Even on cooler days, such as today where the temps are in the lower to mid 80's it cannot cool below 76, and the upstairs is at least 78.

We are schedule to have a tech come out later this week from the company that installed the updated AC, but was hoping to get some tips here and possibly some good questions/things to look out for when I talk to them.

Thanks in advance.

Jason

p.s. we've had some people suggest getting duct booster fans, but I have not installed them as I do not know if they would really benefit.