We completed construction on our home in Florida in 7/2006. We have 2
Bryant central air units (one 3 ton unit and one 4 ton unit). Last
week I noticed the 3ton unit couldn't keep up with the cooling during
the afternoon hours.
I called the A/C company that put the units in during construction.
Here is what happened:

Visit 1: (last week): the tech tells me the system is low on freon
either because it was never filled properly or there is a leak
(they'll test for the leak if it gets low again and the problem
resurfaces). I received a bill for $90 and was told the unit would
catch up that night then should be fine. The tech noted that air was
now coming out 16 degrees cooler than when going in so I should now be
fine.

Visit 2: after I called and advised there was no change the boss sent
out his "best diagnostician" who "made some adjustments" with the air
handler which is up in the attic and noted we now had 18 degrees of
cooling and the unit would be fine once it catches up tonight, but
again there was no change.

Visit 3 (today): the boss decided to send a team to figure it out, the
2 original techs plus one more. They each seemed to have their own
diagnosis of the problem based on what my wife had overheard
(unfortunately I wasn't around the whole time). They had simply told
me the plan was to gather info and have Bryant diagnose the system.
Now I'm told the reversing valve needs to be replaced to the sum of
$720 even though the unit and part is under warranty (I'm told it's a
lot of labor to replace it).

I called another company who will come in the morning for a free
estimate/2nd opinion. They told me the problem didn't sound like
something caused by a bad reversing valve but they'd come out and
see.
I'm looking for any advice on how to proceed with and what questions I
should ask, as I'm looking at a lot of money and not confident these
guys know what the real problem is.