Alfa Romeo Repair: cooling system, diagnostic skills, electrical problem

Question
there is something wrong with my cooling sysetem. cooling fan doesnt come on all the time and thats when it runs hot. doesnt run hot on freeway only in traffic. when it is hot it will overflow all water out the tank. im thinking that it is a thermostat problem but not exactly sure. there is no leaks in radiator or water pump. so what could it be?

Answer
Below 30mph a fan is required to provide enough airflow
across the radiator to cool the liquid in the radiator.
Your problem is that the fan does not come on to cool
the liquid at low speeds.  This is an electrical problem
and requires diagnostic skills to find the problem.
If you would like more information, be specific in your
next message.