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1 pin e-fan harness installation

Your PCM must be programmed for fan activation in order for electric fans to operate correctly. 

*NOTICE: If you receive the incorrect harness please call Nelson Performance IMMEDIATELY! Any harnesses that are modified or installed will not be replaced.

PCMs can utilize fan control similar to the 2005+ GM vehicles.
The e-fans will function on low based on coolant temperature and AC line pressure.
Low speed will activate when the low speed coolant value is met.  If coolant temp has not activated fan control and the AC is turned ON, then one e-fan will turn on HIGH speed.

Before emailing NP for tech assistance, test your harness!
If the harness works as described below, the harness is functioning correctly and the installation is causing the issue.
OR, your PCM is not calibrated correctly for e-fan operation.

Testing the Harness.  Applying Ground to the Blue e-fan harness wire will turn both e-fans on LOW speed.   Applying ground to the Blue wire and 12volts to the Green wire will turn both e-fans on HIGH speed.


  1. Using a 17mm wrench remove the nut from the red battery junction box located on the driver’s side engine.
  2. Locate the ring terminals that fit the junction box.  These wires will be the two red and one white wires.  In order to close the red box, you may have to notch out the bottom of it using wire cutters or a hand held razor/box cutter.  Secure the 17mm nut onto the stud and close the lid.
  3. Located just to the left are the two 10mm bolts that hold the junction box to the alternator bracket.  Remove one of the 10mm bolts and locate the ¼ ring terminals on the harness.  Ground the wires using the 10mm bolt.
  4. Located between the junction box and ground mounting point is a group of wires covered by loom.  Open up the loom and locate the green wire.  To test the correct green wire, a voltmeter may be used to test for the presence of 12 volts when the truck is running and the AC clutch is engaged. Using pliers, crimp the provided red tap to the green wire.  Locate the green wire on the fan harness and attach it to the red tap.
  5. Remove the black cover from the PCM.  This is done by pulling outward on the cover and clearing the two plastic tabs.  Using a 7mm socket remove the blue PCM connector.  This is the connector closest to the engine.  Remove the grey retaining cover from the topside of the blue PCM connector.  (If you have trouble removing the grey cover, simply use some pliers.  A small flathead screwdriver can be used to pry the grey retaining tabs out.)Turn the connector over and using a thin pick or screwdriver, press on the white retaining tabs on each side of the blue-clear cover and remove it.  Lubricate the blue PCM wire on the harness.  Simply push it through pin 42 until it secures itself.  Pull on the blue wire to ensure it is secure.  Reinstall the blue-clear cover and grey retaining cover on the PCM connector.  Reinstall the PCM connector.
  6. Locate the LS1 fan connectors on the fan harness, install them and connect to the fans.  Be sure to secure the wires with tie straps.
  7. Using the supplied screws, attach the relay connectors to the upper left corner of the PCM cover.  Be sure to clear the PCM when installing the screws 


Flex-Fan or Universal Fans:     

The fan harness will have four power wires coming from the relays.  They are grouped in a wire loom and are attached to your existing fan motor wires using the supplied butt connectors and heat shrink.  Be sure to cut the heat shrink to the appropriate size and install it over the wire before crimping the butt connector.


The four wires are grouped in pairs.  Each pair belongs to one fan.  Do not tie the pairs together or swap wires.


Verify harness is installed correctly: 

Start the truck and turn the AC on.  As soon as the AC clutch engages, one fan will turn on high.  When the engine coolant reaches the desired turn on value in the PCM, the other fan will turn on high.  If the AC is off and the coolant reaches the turn on value, both fans will turn on low.