What engine is the car
If it is overheating when you drive along at around 40-50 on a light throttle then chances are that it is nothing to do with the fans or the sensors as these ony kick-in in traffic or if your really thrashing it as the engine gets to hot and the radiator needs additional airflow from the fans to get the coolant temperature down
This would you leave you with a mechaincal fault in the cooling system, either the thermostat is stuck closed and the coolant in the block doesn't circulate to the radiator to cool down or the water pump is on the way out
When this happened on my A6 (1.8T) it turned it it was the impeller in the water pump (made of plastic???) was cracked so the pump wasn't puming properly.
To get to it they had to take off the timing belt, so it wasn't a cheap fix
