Does anyone know what would cause the electric radiator fan to come on
within a minute or so of starting a cold engine and staying on the entire
time the car is being driven? Sometimes it only takes a few seconds after
starting the engine until it comes on. It is keeping the engine very cool
according to the gauge, and I can't get anything more than lukewarm air from
the heater because of it. I replaced the radiator fan sensor that screws
into the engine block and it didn't help. I replaced the radiator and water
pump and it didn't help. This is an engine that has always been
well-maintained including periodic changing of the coolant. It is a 1994
Beretta with a 6 cylinder.

Is it possible that a piece of foreign material, such as a piece of gasket,
has lodged into a port near the place where the sensor is located? The
engine coolant appears to be flowing freely through the water pump,
radiator, and heater core. If I rev the engine at a very high RPM for around
5 minutes it will finally warm up and the heater puts out good heat, but as
soon as I allow the enging to idle back down the engine immediately cools
down and the heater goes back to lukewarm air.

I bought the car new in 1994 and the temperature gauge always stayed
slightly above halfway. Since this problem started, the temperature gauge
stays way to the left and the fan runs constantly.

Thanks.