I am racking my brain to figure out this problem I have been having with my 10 year old a/c unit, but I cannot figure it out. Every day since it has gotten warmer, my thermostat creeps up at least 3 degrees from the preset temp. I have it programmed to stay at 76, and it goes up to around 79 in the afternoons and stays there until sometime during the night, until it gets it back down to 76. I have checked the Freon, and it is at the correct level. I have about a 16 degree split temp from the vent versus the temp in the house, + or - 3 degrees or so. The attic temp is around 125 degrees around 5 in the afternoon when the thermostat starts to go up. I have checked the vents and they are all putting out air, so no ducts are disconnected. I have checked the return and it is pulling air at an acceptable rate with a clean filter. All the windows and doors are shut and I do not know of any leaks in the house. Even when it reaches the desired temp of 76, it still runs for what I think is an inordinate amount of time before it shuts off. Could the thermostat be bad? It is a 10 year old electronic one. I am sorry to be so long winded, but I wanted everyone who reads this to know that I have done my homework, at least I think I have, and I am posting here to hopefully find someone who may be able to shed some light on what may be causing the problem before I spend money on a service call. Thanks in advance for any help you all can offer.