2001 Mercury Villager where is it?

Thank you for the reply. The book said the sensor was next to the sending unit. I did notice this sensor while troubleshooting. However, the sensor that the parts store sold me is different than the one at this location. Can you bypass this sensor and make the fan come on? How do I isolate the problem to this sensor? I know that there are some relays invlolved in this circuit as well. Again thank you very much. I am an electrician. So if I can help you let me know.

Thank you very much for all of the info. Im sure that I can solve the problem with all of your help.

Im having a hard time. The sensor that is described as being the ECT (elect. Cooling temp sensor) with the Ltgrn/red wire and blk/yel wire when bypassed with a paper clip does nothing. I straight wired the fan from the battery and it works fine on low and high. Voltage on the two pins of the plug is 4 volts. Book says its supposed to be 5. Is that the issue? I dont think so. From coresponding with another guy on yahoo, there is possibly another sensor that actually controls the fan. It is supposed to be located on left rear of engine. Could someone please tell me where that is? I take it as being on the firewall side of motor drivers side under intake plenum. I have torn the air induction plenum and throttle body down and out of the way and cannot locate a sensor. Someone please help me before I set this van on fire. Do I have a pcm problem maybe? Im pretty good with a wrench. Nobody at my local Napa, Oreily's, or Advanced Auto can give me any help. Im trying to help out my grandfather and get this thing on the road and out of my yard. As you can tell Im frustrated. The haynes book is wrong and of no help. Chilton supposedly does not make a manual.
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jwb