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My daughter's 95 Taurus 3.0 6cyl electric cooling fan won't shut off. We had this problem about 4 months ago and I changed the control relay and the problem went away. Does anyone have any idea what could cause it to come back. tonight I'm going to pull some codes off of it and see what that says, I know it'll have the DTC 543 it always does.

Any advice is greatly appreciated.
 

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Looking at the wiring schematic for this system, it seems the only way the fans will run in the engine off position is if the intergrated controller relay is shorted internally. During normal operation, the pcm monitors engine temp and a/c operation and commands the fans on when needed. When the engine is shut off, the relay still has power on at all times through the 50 amp fuse in the engine fuse box, but should not have any output unless the relay is closed internally by the pcm. Hope this helps.:yesnod:
 

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Well I guess if the fan motor is overdrawing it could "weld" the relay points closed. Seems like it would melt the soldered circuit board first tho...
 

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So I looked up DTC 543 and got...
When the PCM commanded the fuel pump on, voltage was not detected on FPM.


If I recall correctly, the CCRM also includes the Fuel pump relay.
 

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Without taking the time to look at the pin out diagram, I wondered if there was any possible way that the connector is in upside down? I kinda suspect that is not possiblle, but if it is then would it be worth it to track back how things would be connected backwards upside down?
 

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The connector is keyed and connot be plugged in backwards.
 

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Thanks BogHog, I suspected that it was keyed, but didn't know for sure.
 
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