I just bought a 2 story 2400 sq.ft. house and I find that, even if noone is going in and out during the day, the A/C can't maintain 74F during the day. On a sunny day, the temp will creep as high as 80, starting from 74 in the morning, before the evening comes and it starts to cool down again. The A/C is a single York and I don't know the size or age of the unit. Where do I look for this info? I do know that the filter for the return vent is a 20x30, and I think it is too small, since a new filter is bowed up from airflow as soon as it is put in place.

I have a 609 cert and have been doing automotive A/C for over 10 years, but I don't know much about HVAC. I am assuming the refrigerant is R-22, since my R12/22 manifold gauge connectors fit. The pressures last night, with it being 76 in the house and 82 outside, were 60 and 165. I was wondering if this indicates a problem such as low refrigerant.

We have a home warranty, so I can will call them if I have a problem, but I'd like to know a little about the problem before calling them in.