P0128 code

Yesterday I went to the store and noticed my air conditioner was blowing out hot air. And noticed that the engine fan was running hard. I run a obd meter and git a code p0128. I checked the coolant level and it was low so filled it up. Ran the car fir a bit to see if the that solved the problem it did not but it needed coolant. I reset the engine code to see if it would created the code again and it did not but the air conditioner blew cold air again. Drove all night for my job. No problems got home ran the obd again no code. Went to bed got up went to store and noticed the air conditioner was blowing hot air. I checked the coolant level again it was fine. Ran the obd again and got the p0128 again. I reset the code again and the air conditioner worked fine. I changed the thermostat and sensor last year what is going on.