My Ac is blowing out hot air instead of cool

[Aimee]

I have Thermostat set to cool 82, it will work fine then all of a sudden my ac seems to continually run and the thermostat starts to go up to 84, 85 and warm/hot air blows out of vents. I had my contact, fan motor replaced and thermostat. I had 2 different guys come out, told them my problem. One changed the contact and the other changed the Fan motor in condenser unit. They both tested compressor and it tested good. freon tested good. Fan on thermostat set to auto. Air filter is clean and outside unit is clean. Does anyone know what problem is? It's almost like something misfires and it continues to run so long that it starts blowing heat out. I don't think, when it does this it would ever turn off unless i turned the thermostat off. It does work, but several times today it didn't work. Sometimes I can go a whole week without having a problem. When it happens I have to turn thermostat off wait 15 min and turn it back on. Then it works again but sometimes i have to turn breaker and everything off and water the coils i believe thats what it's called on the condenser unit outside. I have a York. I'm concerned about calling another person out and them not fixing the problem. I could get a whole new unit but doesn't mean the problem will be fixed, what happens if the wiring to thermostat is bad are something like that and I just bought a whole new unit. That would be horrible.