Chrysler Repair: Radiator fans dont come on., coolant temperature sensor, chrysler town and country

Question
1997 Chrysler Town and Country van with 3.8 liter. Hard wire the fans and they work. There's a heat sink relay mounted to the frame rail down below the (&$#@*) air cleaner housing. I need to know how to shoot the system to find out what needs to be replaced. I just bought the car at auction abd don't know the history except that it has 150,000 miles on it. Thanks...

Answer
Hi Gene,
I am a bit short of info on years after '95 (and that I haven't worked on Chrysler vans) but based on the wiring diagrams for those earlier years for the 3.8L I can suggest the following:
There is a fan relay in the power distribution center. The activation coil of the relay is powered by a white wire that should have 12V on it when the ignition switch is "on". The other end of the coil is controlled by a number of possible sensors which activate the relay by grounding the dark blue/pink wire. One of those grounding functions is done by the engine controller which takes its cue from the coolant temperature sensor located on the top left of the engine next to the thermostat housing. That sensor has a tan/black and a black/light blue wire. You might begin by checking that the sensor is working: it should have a resistance of 7,000 to 13,000 ohms when cold, and when the engine is a operating temp (200F) it should read 700 to 1,000 ohms. If it doesn't drop to that lower resistance level, then it won't cue the controller to ground the relay coil. The other possibility is that the relay's switch points are corroded or the coil isn't actuating the switch. The power for the fan is present all the time at one socket of the relay, brought there on a gray wire from a 30 amp fuse in the power distribution center. So I would suggest checking for a fan fuse in the power distribution center. The power to the fans is brought out of the power distribution center on a light blue green wire to the motors (I guess you have found the disconnect in order to verify that the motors are o.k.)
Thus the possibilities are: blown fan fuse, defective coolant sensor, defective fan relay, and of course there could be a problem with the wire interconnecting these items but we'll hope it isn't that.
I am not sure what you mean by "heat sink relay mounted to the frame rail down below..." but if that is the coolant temp sensor so be it. Check the color codes on the sensor wires to verify that you found it
Let me know what you find out. I'm using a '91 manual as a reference which shows the 3.8L as used in the Fifth Avenue car. But I would expect a very similar fan control system would be used in your van.
Roland