Part of the problem could be from the wall acting as a heat sink. This would effect the thermostat operation but it would not stop the unit from cooling correctly. It would cause errors in both the sensed temp and the read temp on the dial. That is why a separate thermostat should be used for all temp readings.

Hi, T-Top and HVAC1000

I just wanted to thank you and let you know how this ended up.

First, I want you to know that you were right about the pressure not being correct. The builder called another A/C expert from an outside firm who determined that the pressure was too low - the difference between the intake and the output was only 16.

After these tests were done the builder agreed to replace the 1.5 ton unit with a 2 ton unit at no cost to us.

Thanks so much for your outstanding information and advice. I just wished that they would have listened two weeks ago.

Your doing a great service for people like us and I don't know how to thank you enough.

Tom, Brigitte, and Steven White

Is the return air grill located centrally in the condo? If so, the stat should be near it to measure the air returning. The stat needs to be on an inside wall, free from drafts including supply vents blowing on it. A different thermostat probably wouldn't help. And you have the 16th floor issue... roof heat and heat from below. Does the air conditioning cool the unit, despite what the thermostat does or is the false reading over cooling the condo?