Yea mine was a pain to get is sealed but after you do it's good. Getting the temp from engine is not ideal because the thermostat will be closed until it reaches the opening temp then it circulates the coolant threw the radiator. If the temp(on the controller) is lower than the opening of the t stat it will turn on the fans when the coolant is not being circulated(threw the radiator). Getting the reading from the circulated coolant is more accurate. Putting the sensor in the cooling fins should work but getting the temp direct from the coolant would be better. If i where to do this again i would opt for a controller that uses a thermistor sensor rather than a mechanical thermostat. This one just happened to come with the fan.