The fans running 100% of the time is unusual but that itself will not cause an overheated condition. You might just have a stuck thermostat. But running that much might cause them to fail sooner. Also note that the heater controls set for "Defrost" will activate the fans. (Defrost turns on A/C and fans.) A simple test is when the car is stone cold, heater controls turned completely off, start motor, fans should be Off. If they are On, a temperature sensor is sending an incorrect signal to activate fans when not needed. Sensor needs replaced. Hope I didn't confuse you. Been a mechanic 50 years....
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