Radiator fan heat sensor switch wont turn on?

There are two different thermostats--one in the cooling system, and one just to turn on fans. The AC has a separate circuit to turn on fans regardless of engine temp, so tind the the fan thermostat and test it.

Follow the wiring from the fan motor it should lead you to the heat sensor that is located on your radiator, this sensor swithch as possibly stuck in the closed circuit position that's wye your fan is running constantly as this switch completes the power supply to the fan you can pull the spade clip of the sensor to stop the fan until you get a new switch sensor.
Good luck

check coolant level is up to the mark, then locate radiator temp sensor switch ( on the radiator ) and check connections, you can by pass the switch in the wiring plug to ensure the fans work, if fans operate the radiator sensor switches are probably at fault and will require renewal

Turn vehicle off. Allow to cool. Raise hood.
Try to see if the fans spin freely by hand. If not, replace. If they do spin, proceed to next step.
Next step-
Check coolant level, add if needed. Remember-radiator must be cool before opening cap. Make sure radiator cap is secure and tight if coolant was added.
Start vehicle. Observe coolant gauge as vehicle warms. Fans should come on when temp gauge reads halfway between c and h.
If fans do not come on see if they come on when you turn on ac or heat. If doing this makes them come on, suspect faulty cooling fan sensor switch. If they don't come on replace cooling fan sensor switch and fan relay.

What size engine?

The fan is controlled by a heat activated switch which is installed in the radiator. The switch turns a relay on which powers the fan. Locate the switch in the radiator ( in the bottom tank) and join the two wires together, this should start the fan. If it does then the switch is faulty, if is does not, check the relay and fan motor..

Dodge Caravan is notorious for failure of the electronic cooling fan control module (AKA cooling fan relay). This is not a "relay", it is a solid-state control unit, but many people call it a relay anyway.
It is mounted on the inside of the left frame rail just behind the radiator. You have to look up from UNDER the vehicle to see it. It looks like the picture below. The picture shown is very close to actual size.

It wont hurt anything if they stay on all the time cus the fan will mostly runs off your alternator. But if does bother you then it meant be the sensor on the fan. Or you can install a switch to turn the fun off and on with a toggle switch. But its up to you. But for the most part as long as the fan keeps going to cool off your radiator you should be ok. But i am thinking it maybe the sensor not telling the fan to shut off and turn on when its suppose to.

I own a 1997 caravan and had the same problem, turns out there is a fan relay switch mounted on the inside of the drivers side frame rail under the battery tray.. cost me 80.00 hope this helps..

change the sensor /switch in radiator trace wires back to relay and then wire through ign switch so when you take key out it goes off .