Chrysler Repair: Engine Cooling Fan doesnt come on when needed: 3.0L, lebaron gtc, chrysler lebaron

Question
My Electric Fan quit working on my 1995 Chrysler Lebaron GTC (Conv.) with 3.0L Engine and the engine overheated.  I replaced the Fan Motor and it works fine as long as I turn on the Airconditioning.  The Fan will not run otherwise?  Is there a Cooling Temp Sensor that turns on the Fan and if so where is it located.  All I found was the Fan Relay.  

Answer
Hi Doug,
Yes there are two temperature sensors located next to the hemispherically shaped manifold on the top of the engine which has the top radiator hose attached to it. One has a single wire and is used to operate the temperature gauge. The other one that has two wires that should show a variable resistane (voltage rading) to the engine controller which then would appropriately turn on the fan via the same relay and circuit as is used by the A/C's activation. That coolant temp sensor's wires are black/light blue and tan/black. The resistance between the contacts at the plug socket should be 7,000 to 13,000 ohms when the engine coolant is at 70F and then drops to 700-1,000 ohms at normal operating temp (200F). Above that temperature the ohms should drop further which provokes the relay to be energized by the controller. That sensor also is used to adjust the fuel/air ratio. The tan/black wire goes to pin 2 of the 60-way connector at the engine contoller, and the black/light blue comes from pin 4 of the same plug. The former returns the variable voltage, the latter is a 5V reference source used by it and many other sensors. So check that sensor's resistance. Also if you run the engine and then pull the plug off the sensor, the fan should start to run. That is a check of the wiring, without having to deal with the 60-way plug. The normal fan control is that it will come on when the temp is 210F and the vehicle speed is under 40 mph, and if it at a speed of over 40 mph the fan will not come on until it reaches 230F.
So check it out and let me know if you need more help.
Roland