I bought my house last year and my unit worked fine. I noticed tonight it's not cooling. I hear the fan blowing (it's set to auto and cool) but it is not cooling. The thermostat is set to 78 but it's was very hot in my house. I did an override and set the thermostat to 70 but a few hours later I noticed the temperature was 84. I turned the unit off then back on again with no luck. I hear it running but I'm not hearing it "kick in"the way it does when it starts to cool. Please help!