I recently turned off power to my a/c unit to clean filter and now I have replaced the thermostat due to a/c comes on well above the set degree. Still having problems since changing thermostat.:confused:

You did not mention what type or model thermostat you have. YOu do not have it set up properly. If you have the intructions for it read to set it properly. If you do not have instructions look at the " sticky" at the top of theis forum. Much useful info there. Good Luck