Last week I noticed my inside fan was not cutting off and the air it was blowing was not cool. I also noticed the outside unit was not running. I called a friend who used to do HVAC work and he told me it was the contactor. I replaced it and everything works fine until nightfall and then the outside unit will not start up. I have tried but not detected any sounds from the outside unit when this occurs. I will turn the system off and then when I restart it the next day it works fine again until nightfall. I have also changed the thermostat thinking that might have contributed to the problem. Anyone have any thoughts on the situation. I am hesitant about calling a service tech after being gouged by one a couple of years ago.