//******************************** Regulate Soil Temp ************************************
ST = sensors.getTempC(Soil_Temp); //1.03
//CPT = sensors.getTempC(Compost_Pile_Temp); //1.03
if (ST <= Soil_temp_on) // 68°
{
digitalWrite(compost_fan, LOW); // is LOW fan off?
}
if (ST >= Soil_temp_off ) // 70°
{
digitalWrite(compost_fan, HIGH); // is HIGH fan on?
}
This section?
Have you placed some Serial.prints to prove the value of ST is correct and is changing as it should?
Are 68° and 70° correct?
Is LOW fan OFF and HIGH fan ON?